Diagnosing Fuel Pump Issues

[hutch]

There are a number of threads related to fuel pumps but usually the pump is mentioned inside of a "won't start" thread. While my truck would qualify as a "won't start" candidate (by the fact it's sitting in my garage and I had to have it towed here ;) ) - I thought I'd try a thread that is specifically around how to determine if the pump is bad or it's something else that controls the pump (wiring, relays, etc.)

Can someone look at this list and let me know if there is anything else I can do to diagnose? My truck is sitting in my garage unloved and unwilling to start at the moment :(

Summary:
I parked my truck and came out to drive it again an hour later and it wouldn't start up again. I cranks but seems to be choking for gas. I cannot hear the fuel pump humming when I turn the key to the start position. I also don't have fuel pressure (no gas) when I turn it to start and press on the valve near the injectors. There are no codes being thrown and no check engine light.

With those 2 big items it seems that my fuel pump is either dead or that a wire or relay is preventing it from turning on.

I've gone through the forum and tried to consolidate the items that could cause a fuel pump to not function - or at least how to determine if the pump is completely dead. The should be in order of ease:

Fuel Pump Fuse: I CHECKED THIS AND IT LOOKS FINE
15A fuse in the fuse box under the hood on the driver's side. I checked it and it looks fine.

Inertia Switch:
(snipped from another thread) ...Did you try and reset your inertia fuel switch under the hood, center, near firewall? (Push the button on top). If that doesn't work try, by-passing it with a paperclip in the plug end. (If still no start, you've at least likely eliminated the inertia switch as the culprit.)

Fuel Pump Relay: HOW CAN I DETERMINE IF THIS IS MALFUNCTIONING? Also I opened the box and didn't see it from the top.
From what I understand, in the 1997, unlike the 1995s, the pump is controlled by a special multi-function relay. (NOT one of the 9 relays inside the cab right?) It is located under the hood on the passenger side inside/under the "white box." I'm assuming there isn't much you can do here to test thing right? Here is the item at AB - RELAY - FUEL PUMP - MULTIFUNCTION Item: YWB100820LG Genuine Part
http://www.roverparts.com/Parts/YWB100820LG.cfm

Change Fuel Filter:
Worth a shot. I don't know if a clogged fuel filter would actually prevent the pump from turning on. I'm going to try this later today. For me specifically I changed the fuel filter only 8 months ago. I can/should give that a shot but I can't imagine that's it(?). I hope so.

Fuel Pump Wiring: HOW CAN I SEE THIS WIRING? HOW DO I LOOK AT THE TOP OF THE TANK?
(snipped from another thread) ...figure out if the fuel pump plug end itself is corroded. There are 4 wires that run to the plug connecting to fuel pump: Purple/White is fuel pump power; Green is fuel guage power, and two Black ground wires.

Other Items:
Ensure there aren't any check engine codes, reset the codes with an OBDII reader, disconnect the batter leads for a while then reconnect.

Finally I know that the mass air flow sensor might come into play along with other fuel-related devices. Other items, to me, might prevent the truck from starting or cause it to die a mile down the road but when the truck cranks but won't start AND I can't hear the fuel pump then I have to think it's related purely to the pump and controlling items (above).... right?

Thanks for any advice... I'm especially interested in how the hell to see the wiring on the pump itself without dropping the gas tank. Is this possible?

Hutch

[jdempsey]

I had a similar problem and it turned out to be a fuel temp sensor..simple and cheap. I did all the check symptoms, changed fuel filter, changed fuses ect

[evilfij]

In a 1997, I would not be concerned about the relay (never heard of one go bad). If you are getting no gas (ie not even catching a little when cranked) and can't hear the pump, it pretty much has to be the pump or the wiring to the pump. So how full is the tank? Ever drop one before?

[hutch]

In a 1997, I would not be concerned about the relay (never heard of one go bad). If you are getting no gas (ie not even catching a little when cranked) and can't hear the pump, it pretty much has to be the pump or the wiring to the pump. So how full is the tank? Ever drop one before?Good to know about the relay in the 97. I've been stranded by the relays in the 95s going bad - simple fix.

The tank is pretty full actually - just over half I think. I've never dropped one before - uggh. It's been a while since I've pulled the black mat in the tub back but if I recall you can't remove the bottom panel separately. Would have been a good idea to leave an access hatch for that LR!!! :angry

There isn't another way to check the wiring?

I'll have someone try to start the truck while I check the valve just to be sure but I'm pretty confident it's not getting any pressure.

Also - I'm assuming it's not really realistic that a bum fuel filter would prevent the fuel pump from running right?

FYI - Jason - good tip about the temp sensor. I found it in the manual and will locate it and if cheap enough it's worth a shot.

Hutch

Follow-up Post:

I had a similar problem and it turned out to be a fuel temp sensor..simple and cheap. I did all the check symptoms, changed fuel filter, changed fuses ectWould that prevent the pump from even firing up? I could see it killing it one the sensor goes off (or is bad) but I would assume the pump would start and then be killed. Just a guess.

Found it on AB:
http://www.roverparts.com/Parts/ETC6661.cfm

I feel like each possible component is about 100 bucks. If I bought them all I might as well have taken it to he local LR shop! Eeek.

[evilfij]

The wiring does run back there and I believe there is a junction that can go bad, but that might be on a RRC or earlier truck and I honestly don't know.

One other thing to check is the inertia switch which would be an easy fix.

[hutch]

The wiring does run back there and I believe there is a junction that can go bad, but that might be on a RRC or earlier truck and I honestly don't know.

One other thing to check is the inertia switch which would be an easy fix.I *think* I see where the wiring veers off from a thicker bundle of wire but it looks good at the junction point. Regarding the inertia switch - do you just mean reset it by pushing it down? Someone else had mentioned bypassing it using a paperclip but I'm not sure how to pull that off. Just pushing it doesn't have an effect unfortunately.

[evilfij]

You could bypass it, but it is unlikely that it is the cause. Check the junction on the fuel pump wires. Unless someone else has any bright ideas, I would start dropping the tank and run power directlty to the pump to see if it is bad.

[LRover]

Are you sure that its not getting fuel? Check for fuel pressure (32-36psi) at the fuel rail. When you first crank the engine the fuel pump should run for only a few seconds to pressurize the system until engine start then it runs continually. If it is doing that then most likely the fuel pump is operating ok and I would look another issue

[hutch]

Are you sure that its not getting fuel? Check for fuel pressure (32-36psi) at the fuel rail. When you first crank the engine the fuel pump should run for only a few seconds to pressurize the system until engine start then it runs continually. If it is doing that then most likely the fuel pump is operating ok and I would look another issueI tried 2 things.

1. I attached a bike pump (!) to it and cranking the engine didn't make the pressure needle jump at all. (Not sure if this is a ridiculous way to test.)

2. I then simply pushed down on the needle on the valve and had someone try to start it - no gas/air coming out of the valve.

I think it's dead or something else is the culprit. Thanks for the idea - any other advice is welcome for sure...

Follow-up Post:

You could bypass it, but it is unlikely that it is the cause. Check the junction on the fuel pump wires. Unless someone else has any bright ideas, I would start dropping the tank and run power directly to the pump to see if it is bad.I'm pretty hands-on but after reading over the workshop manual seems like a job for a couple people and not something to take lightly or just as a quick test. I'm starting to think this has to be it - either wires or dead pump but I'm going to use this as my last resort and probably will have to tow it to the dealer (who has stuck it too me at least once or twice). Any other advice is welcome. I'm hoping for that silver bullet... perhaps a "flux capacitor" at advance auto parts?

[evilfij]

You can syphon off most of the gas to make it easy to remove (remove the big filler neck end of the rubber hose and stick the syphon hose in). If yours is a florida truck, it should not be hard to get out, only time consuming.

I am trying to think, the only other thing I can think of that gets power to the fuel pump is the ECU.

[hutch]

You can syphon off most of the gas to make it easy to remove (remove the big filler neck end of the rubber hose and stick the syphon hose in). If yours is a florida truck, it should not be hard to get out, only time consuming.

I am trying to think, the only other thing I can think of that gets power to the fuel pump is the ECU.Regarding the ECU, I checked with an OBDII reader and it isn't throwing codes so I *think* it shouldn't be that.

One thing to note is that it WAS a MD truck for a couple years of its life so there are some - not a lot - rust spots. The one item that does have the most is the damn skid / gas tank cradle. As a matter of fact when putting in shocks/springs last year I snapped the bolts off the sway bars.

I'm assuming if I drop the tank that it would be a good time to replace the skid / fuel tank cradle/guard? I don't mind getting charged labor - assuming I'm not doing this myself - but I'd hate to get killed on the fuel pump and guard at dealer prices. I'd rather walk into the dealer with the parts - or order then next day air once the truck is there. Also the fuel line connectors have a little rust. If it turns out it is the pump does it make sense to replace the lines, fuel tank guard as well as the pump?

[rover4x4]

just be generous with PB Blaster, my truck was a Fl for 85% of its life, it was in PA for a little while. I havent had any rust issues.

[evilfij]

Regarding the ECU, I checked with an OBDII reader and it isn't throwing codes so I *think* it shouldn't be that.

One thing to note is that it WAS a MD truck for a couple years of its life so there are some - not a lot - rust spots. The one item that does have the most is the damn skid / gas tank cradle. As a matter of fact when putting in shocks/springs last year I snapped the bolts off the sway bars.

I'm assuming if I drop the tank that it would be a good time to replace the skid / fuel tank cradle/guard? I don't mind getting charged labor - assuming I'm not doing this myself - but I'd hate to get killed on the fuel pump and guard at dealer prices. I'd rather walk into the dealer with the parts - or order then next day air once the truck is there. Also the fuel line connectors have a little rust. If it turns out it is the pump does it make sense to replace the lines, fuel tank guard as well as the pump?


There has to be an independent near you that would change the pump and do a new skid plate for you. ECR has alloy skidplates for $225 on the website, but I don't know if Mike would ship you one.

Ron

[hutch]

There has to be an independent near you that would change the pump and do a new skid plate for you. You read my mind. Actually I've worked for a long time with a guy here in the area but Rovers are his passion and don't pay all the bills so it's tough - weekends only really and I don't want to drag this out as it's not a "project" truck ;). There is a shop literally down the road that I've seen Unimogs and Pinzgauers parked out front. I also have a friend with a lightweight that they've done work on so I'm probably going to give the shop a shot and see if I can build some trust. If anyone knows of a good shop in the Tampa Bay Florida area I'd be interested in knowing in case this doesn't work out.

I'll post the outcome. Thanks for the ideas.

Hutch

[dbj2003]

I seem to have experienced a similar problem. Please let me know how things go. There is what looks like a plastic hose coming up out of my fuel tank that has been cracked and creased. Not sure if this could have led to or contributed to a fuel pump issue. Having my shop take a look this time as I'm sick of dropping the tank myself and want to get it running again asap. It has been choking out on me occasionally leading up to today. Now it doesn't sound like the pump runs at all. I'll let you know when they find something.

Brandon

[Roadsiderob]

Quick question before you drop the tank....does the check engine light illuminate when you turn on the ignition (bulb check) and then go out....or is it nonfunctional? The reason I ask is that the main relay on a GEMS motor (located near the ECU under the hood) is a combined relay that energizes both the fuel pump and provides power for the ECU. If your check engine light isn't working at all, it really could be a bad relay. There are a bunch of connectors next to the blower box under the hood. One of these should be a 2 pin connector with a green/black wire (gas gauge) and a white/purple (fuel pump). If you unplug this connector, you can check for power on the white/purple to confirm that the fuse/relay/inertia switch are working as well as ohm check the pump. I recently had a D90 with a random no start problem and the issue was with water in this connector. It is a convenient place to split the system for diagnostic purposes.

[hutch]

Quick question before you drop the tank....does the check engine light illuminate when you turn on the ignition (bulb check) and then go out....or is it nonfunctional? The reason I ask is that the main relay on a GEMS motor (located near the ECU under the hood) is a combined relay that energizes both the fuel pump and provides power for the ECU. If your check engine light isn't working at all, it really could be a bad relay. There are a bunch of connectors next to the blower box under the hood. One of these should be a 2 pin connector with a green/black wire (gas gauge) and a white/purple (fuel pump). If you unplug this connector, you can check for power on the white/purple to confirm that the fuse/relay/inertia switch are working as well as ohm check the pump. I recently had a D90 with a random no start problem and the issue was with water in this connector. It is a convenient place to split the system for diagnostic purposes.I know the mutlti-function relay you are talking about (or I should say I was told about it during this research.) I can see it under the hood buried inside the white box/cover. Yes the check engine light comes on and then goes out as it should. Interesting to know if it didn't that the multi-function relay could have been culprit.

As Ron pointed out while it's possible it's probably pretty unlikely that that is the issue because they don't go bad that often (unlike the little box relays that have left me stranded before in my 95.) In a way I hope that's not it because I will have certainly gone to a lot of trouble just to replace a simple part!

The truck is now in good hands at a nearby shop that has worked on old LRs, Unimogs, etc. They should know something today and I'll post my findings.

Thanks for the input,

Hutch

QUESTION: What is to be expected in labor/parts if the shop needs to drop the tank and replace the pump? I think the pump kit is around $250 from RN and if I need to replace the skid-plate for the tank due to corrosion that's another $250+. Just not sure about the labor. I haven't worked with this shop but a friend has. Just hoping they are fair - doesn't have to be "cheap."

[hutch]

Well as annoying as this is I towed it to the shop only to find that when they tried it the next day it started up and hasn't had the problem since. The shop has been driving it around all day today.

This is really frustrating because the truck had sat OVERNIGHT in my garage and failed to start the next day after trying multiple times (warm and cold.)

I'm going to replace the crankshaft sensor to rule out that as a possibility.

I guess in theory it could be a soon-to-die fuel pump but I thought fuel pumps usually just go and don't usually show signs of "I'm about to die" but I could be wrong.

[evilfij]

Don't worry, it will do it again. ;)

[dbj2003]

Take a look at your Mass Air Flow Sensor and check for debris or a busted up screen. This seems to have caused (at least part of) my issue. The symptoms were the same. As a follow up, these sensors are expensive, can they be repaired? Anyone ever replace the screen on one?

[evilfij]

Used ones are like $50. 1994 cross with most 14CUX trucks and 1997s I believe (someone would have to double check) cross with GEMS disco Is.

[hutch]

Thought I'd provide an update on this drama - plus I know Ron is going through something similar right now.

My drama continues....

I ended up replacing the crank sensor purely from a "what the hell + good maintenance" angle. While getting that shipped from AB the shop where I have the truck called and said "we nailed it, it has to be the 1997 fuel pump relay" ($100 part from AB). They felt very sure - said that they were getting spark but that the fuel pump wasn't getting power and that when they cooled the relay down (in the fridge...) that it fired up again. Coincidentally I had personally seen the mechanic driving around town that day near the shop so thought he fixed it...

Got there paid the guy and the truck choked - finished the gas in the lines - and then didn't start. Back to square one!

My only thought was that when he said "fuel pump wasn't getting power" he means it didn't make a sound. So perhaps this is a bum fuel pump and/or wires back there and that the relay WAS sending power but nothing working to use that power.. When he calls today hopefully I'm going to find out exactly what he did to determine there was no juice at the pump.

I pressed the intertia sensor plenty of times but I have not bypassed it during a no start - I'll make sure he's doing that. as well.

If anyone has any other ideas as to what else it could be I'm all ears.

[evilfij]

Sounds like a bad fuel pump frankly. How many miles are on it?

[hutch]

Sounds like a bad fuel pump frankly. How many miles are on it?55K Miles

It will start one time drive for a mile then cut out. That's when he says there IS spark but no power to the pump (again, I'm hoping he literally means no power not just no fuel pressure or he's heading down the wrong path) which led him to say that it was the relay. I've swapped the crank sensor and the main fuel pump relay under the proverbial white box in the engine compartment. It will then sometimes turn back on an run for a while and sometimes it won't after it dies - really strange.

He now says that a bad pump could be killing the relay - not sure I buy it - does that sound like a possibility? My feeling is that I'm probably going to have to take the plunge and have him drop the tank and replace the pump. I'm assuming at this point it's unlikely that it would be loose wiring at the pump - seems to me that if it were wiring it wouldn't be *that* intermittent and perhaps some shaking of the wires could start it up (?) which is doesn't.

Glad you found your issue though!

Hutch

[cgalpin]

Hutch if you suspect it's wiring then bypass that to prove it. You can cut the wires that run to the fuel pump just forward of the tank above the rear axle (or remove the relay and fuse and just splice into it, but this doesn't' isolate it). Run a dedicated ground and power direct from the battery and test drive. If this resolves the problem, work backwards. It's a hell of a lot easier and cheaper than replacing the fuel pump.

That said, replacing the fuel pump isn't a bad preventative measure :)

[evilfij]

Have you checked the VSS?

[Roadsiderob]

Double check the connector by the heater box. It's a 2 pin connector with a white/purple and a green/black wire. It's in a spot where water can drain onto it from the hood seal and it is one of the cheap Econoseal connectors....like the kind on the rear taillights that always get full of water. Check this connector for water ingress/green growies on the terminals. If it corrodes it can cause the issues you are having.

[hutch]

Fun I get to replace the pump. Apparently it did end up being the pump itself (which has stopped flailing and died "officially") according to the shop. I would have had the truck back this weekend but the tank skid-plate has enough rust spots that he thinks I should put in a new one. Normally he likes to repair them but he said this one should go.

If I essentially can replace it with stock or stock equivalent (not used as an off-road truck that often) does anyone have any recommendations? I'd prefer a bolt-on as opposed to something too custom as I haven't worked with this shop before. I don't mind paying a little more if it's worth it but I also don't rock crawl in this truck!

http://www.eastcoastrover.com/Fuelskid.html (I can see if ECR will ship)
http://www.roversnorth.com/store/p-4817-proline-galvanized-cradle-fuel-tank-defender-90-nas.aspx
http://www.roversnorth.com/store/p-3525-genuine-cradle-fuel-tank-defender-90.aspx
http://www.expeditionexchange.com/cart/product.php?productid=19163&cat=376&bestseller
http://www.roverparts.com/Parts/ABPXFT01.cfm?bc=ab

[evilfij]

Yeastie had a Southdown and I just bought one from ECR for Chiquita. Given that you live in Florida, I would buy a stock one if ECR can't/won't ship one.

[jvelador]

I'm still having the same issue on my D90. How exactly did you run power directly to the fuel pump?

[hutch]

I'm still having the same issue on my D90. How exactly did you run power directly to the fuel pump?I personally didn't. A local shop did and I think it's a matter of splicing into the leads in in the rear of the truck running right to the pump. The problem is - as far as I understand - to do this it's easier if you lower the tank a little bit. There isn't much room there (which can cause the wires to get pinched/frayed/broken) to work in. That's the main reason I decided to bring it to a shop and not do this myself. Apparently dropping the tank really shouldn't be a 1-person job.

FYI - I should have the truck back by Wednesday - I'll post and update assuming all is well.

[jvelador]

Thanks, Hutch! I'm resolved to take it to a local shop. I tried yesterday and twice it tried to sputter into life. This leads me to believe there is a loose connection somewhere.

Thanks again,

javier

[hutch]

Well in the end it turned out to be a failing fuel pump.

During the drama I replaced the crank sensor for good measure which wasn't that expensive.

What ticked me off was the garage that did the work then swore up and down it was the fuel pump relay under the "white box" on the passenger side of the engine. As many of you said - that is a VERY unlikely piece to fail - and you all were right. I ended up next-day-airing the sucker to the tune of 150 bucks total just to replace a perfectly good part! Turns out at that time he DIDN"T splice in to determine that there still WAS juice running to the pump indicating the relay was fine.

In the end he did splice in and the fuel pump was the culprit. Quite an expensive little adventure for me.

I hope not to have to post to this thread again saying it was something else!

Hutch

[evilfij]

At least it is fixed.

I am not sure how people owned specialty vehicles before the internet, I guess a club + national newsletter, but without the interwebs I bet half the D90s in the country would not be running right now. :)

Ron

[cellulararrest]

It's both a blessing and a curse. Sometimes it's best to just check the service manual :).

[jvelador]

Thanks, Hutch.

I installed a new battery, a new fuel filter and one new relay this weekend. It sputtered, ran on what appeared to be one cylinder, then died. This happened half a dozen times. I kept thinking the fuel line was simply dry and that if the pump was good, it would prime it after a few attempts.

Can someone tell me where the fuel pump fuse is on a '94? Is it inside the engine compartment or inside the cab. If it is in the cab with the cluster of fuses, which one is it?

I've read different posts regarding fuel pump/relay issues, but have yet to identify it.

Thanks!

[rover4x4]

Did they ever check the pressure at the fuel rail?

[cgalpin]

In the end he did splice in and the fuel pump was the culprit. Quite an expensive little adventure for me.

That's pretty pathetic. I took that step on the trail this weekend as soon as I couldn't hear the pump, and confirmed my relays were good. A quick easy and obvious way to check if the pump itself is good.

At least it is fixed.

I am not sure how people owned specialty vehicles before the internet, I guess a club + national newsletter, but without the interwebs I bet half the D90s in the country would not be running right now. :)

Ron

At least since cell phones they just called a friend ;)

[hutch]

Did they ever check the pressure at the fuel rail?I did originally and didn't have pressure/fuel but I wasn't (personally) comfortable with splicing in to determine if it was the relay or pump itself. I just assumed that's what a shop would do immadiately (he did.... eventually...)

To 2nd Charles comment - I agree. It was pathetic he didn't do it considering I asked him to originally and when it was confident it was the relay I assumed he had. Alas....

Still less expensive than the dealer and probably just as good work. I fault him for jumping to conclusions (and being a bit lazy). I still feel like he knows his stuff.

Thanks for all the advice along the way everyone.

[evilfij]

At least since cell phones they just called a friend ;)

Who turned out to be useless. Any update?

[cgalpin]

Not yet. It's in the capable (but busy) hands of Trevor @ RoverLab who is a AAA tow away in Elizabethtown :)