FAQ: Fuel Pump - General Questions, Compatibility & Troubleshooting

turtleman wrote:

I'm no authority on fuel systems but I would say there are only two ways to go that makes sense. If you are going to be keeping the car to a level that can be supported by 65lb injectors or so, just swap a PRJ's racetronix-walbro pump. 255lph can get you pretty far. If you need or just want more for the hell of it, I'd figure out how to eliminate the in-tank pump or just keep it soley to keep the jug filled and use the inline as the actual fuel pump. That'd require a little custom work on the sender but nothin too tricky.

Maybe Alex or turbo400sbc will chime in here since they set up inline's on rivs.

thanks for that. i am really just looking to take the pump out of the tank all together. i like being able to do repairs without having to dig through the tank itself. major PIA. ill be keeping the stock injectors,i dont think ill be up grading the fuel delivery,just making the car as repair friendly as i can. i know i can gut the oem pump and leave the sender in place. except when the sender takes a crap,which it has been intermittently for some time now,i just dont really need to instal a high perf fuel pressure regulator,i suppose i could but since im not maxing out the oem fuel pressure i dont know if that would make sense.

Here's the reason to keep the pump in the tank - COOLING. Our experiences with high pressure FI out of tank pumps have been replacing about one every year. This is on a retrofitted EFI system to an older car, but it needs 50 PSI like our Rivs. We are going to make an in-tank system to replace the out of tank because we are sick of buying fuel pumps for the car every 12-15 months.

You should not need to access the fuel pump so often that it's causing headaches. It should be a once every 10 years or so access.

deekster_caddy wrote:

Here's the reason to keep the pump in the tank - COOLING. Our experiences with high pressure FI out of tank pumps have been replacing about one every year. This is on a retrofitted EFI system to an older car, but it needs 50 PSI like our Rivs. We are going to make an in-tank system to replace the out of tank because we are sick of buying fuel pumps for the car every 12-15 months.

You should not need to access the fuel pump so often that it's causing headaches. It should be a once every 10 years or so access.

right on Derek - good point I totally forgot about

If the main reason for wanting to switch is serviceability, it sounds like a bad bust. To bad we can't get bad ass billet in-tank units that house 3 pumps like they make for the cobras. For your case, that would be 2 spares that would never have to be touched lol

deekster_caddy wrote:

Here's the reason to keep the pump in the tank - COOLING. Our experiences with high pressure FI out of tank pumps have been replacing about one every year. This is on a retrofitted EFI system to an older car, but it needs 50 PSI like our Rivs. We are going to make an in-tank system to replace the out of tank because we are sick of buying fuel pumps for the car every 12-15 months.

You should not need to access the fuel pump so often that it's causing headaches. It should be a once every 10 years or so access.

wow! i never thought of the cooling thing? let me know how your project turns out.

turtleman wrote:

deekster_caddy wrote:

Here's the reason to keep the pump in the tank - COOLING. Our experiences with high pressure FI out of tank pumps have been replacing about one every year. This is on a retrofitted EFI system to an older car, but it needs 50 PSI like our Rivs. We are going to make an in-tank system to replace the out of tank because we are sick of buying fuel pumps for the car every 12-15 months.

You should not need to access the fuel pump so often that it's causing headaches. It should be a once every 10 years or so access.

right on Derek - good point I totally forgot about

If the main reason for wanting to switch is serviceability, it sounds like a bad bust. To bad we can't get bad ass billet in-tank units that house 3 pumps like they make for the cobras. For your case, that would be 2 spares that would never have to be touched lol

im with you on that one Turtle. there must be a way to instal a say, aeromotive in tank pump for the cooling effect...

What are the symptoms of a failing compressor? I'm having trouble deciding if it's the fuel pump or the compressor. The sound is much more apparent when I stick my head in the rear passenger wheel well as opposed to the trunk area.

I've got a loud whine (though nothing like I've heard from a fuel pump) and it's constant. It doesn't do it with the key turned to ON, just when the car is started and running.

Well sir, the ride level compressor will and does come on with the key in the RUN position without the car started. It takes a few seconds, but it comes on. You would know if the compressor is always on. I've never heard one whine. Fuel pumps, on the other hand, can whine horribly. The FP in my Jimmy whines ridiculously loud, but IDC. As long as it keeps pumpin fuel I could care less

Ugh, definitely believe it's the fuel pump. The tone changes as I press the gas peddle and I can almost make music. Pretty damn annoying. I assume there is nothing I can do short of replacing it? I replaced it just over 2 years ago but I've logged less than 15k on it. Pretty pathetic.

Just a thought, but I'm going to replace the fuel filter. I also see that an airtex strainer is normally stocked. Thoughts on replacing that?

Hell, I'd pull the carpet back in the trunk and start the car. Stick your face down in there and make sure it's the FP. The strainer (or sock) isn't something that you would normally replace unless you were replacing the FP. But, given the accessibility of our fuel pumps, not a bad idea....

It's 100% the fuel pump.

I replaced the fuel filter to no avail. The car has a serious lack of power anything past 1/4 acceleration. It's like the fuel is being restricted. The tone changes in the pump as the pedal changes positions. Not real sure at this point.

A failing pump could cause the lack of power, correct? I assume it may not be pumping enough fuel through. It works fine during light acceleration. Never again will I use an airtex fuel pump.

Yep.....replace the fuel pump. You can put a pressure gauge on the rail and check the pressure. Just see if the pressure goes up with acceleration, or if it moves at all. You only need like 32psi of pressure to run at idle and light acceleration. As high as 60psi is needed at WOT. If the pump can't keep up, it'll fall on it's face like you're describing.

manofmany wrote:

Ugh, definitely believe it's the fuel pump. The tone changes as I press the gas peddle and I can almost make music. Pretty damn annoying. I assume there is nothing I can do short of replacing it? I replaced it just over 2 years ago but I've logged less than 15k on it. Pretty pathetic.

Hey man (omany)...

Thanks to my own declining memory and the barely adequate search engine on our site,

-I'm damned if I can find my own posts about this,
-I'm damned if I can find any posts at all, and
-I'm damned if I can even find any photos that I just KNOW that I took!

However...
It wasn't easy, but a thorough search back through my eBay account and feedbacks turned up some info that can help!

Back when I refused to spend the usurious amount necessary to buy a whole "fuel module" when my gauge sending unit finally wore out, I found these guys and bought the sending unit alone AND a spare pump on eBay...

Yes that's right - a Delco (still chinese, of course ) fuel pump replacement kit for less then $65!
As far as I remember, our '97 supercharged fuel module is the MU-35 (superseded I believe by the MU-1742...) Judging by the goodies in this listing (and the pump with the extra brass outlet for the "venturi pump",) I am correct. However, I communicated with the seller before I bought my sender and pump, and they assured me that they would send the appropriate parts for my application, even though the eBay "application application" didn't include the Riviera.

I haven't used the pump yet, but the sender was correct, and the pump looked identical to the one in my module...

Good luck!
Mark

Thanks for the info. I've come across several parts which I've found to be identical yet the parts application doesn't list the Riviera (coolant tank for example).

I replaced the OE pump because of a failed sending unit as well. Unfortunately, I chose a junk airtex pump. I actually haven't decided what to do yet and am actually contemplating going to the local JY and pulling one for $20.

I noticed there are different part numbers from a 95-96 to a 97. Anyone know the difference and if the pumps are interchangeable?

I looked at RockAuto for '95, '96 and '97, and all 3 numbers are different...

The '95 Riviera had a larger fuel tank, so that probably explains the difference for that fuel module. I know that the '98s are different because they moved the EVAP pressure sensor from the engine compartment to the top of the fuel module. I don't know why '96 & '97 are different, but if I had to guess I'd say that maybe the '96 didn't have the higher-capacity pump with the speed-control module in the trunk.

Yeah, I'm not real sure.

One quick question. All I need is the "module" correct?

http://cgi.ebay.com/ebaymotors/1997-BUICK-RIVIERA-3-8L-FUEL-PUMP-MODULE-NIB-BRAND-NEW-_W0QQcmdZViewItemQQhashZitem5d2d5e2ffaQQitemZ400193105914QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories

This is priced pretty cheap and it surely can't be any worse than the $250 airtex pump that started whining after several thousand miles.

They don't list the MU numbers, but it certainly looks like the correct '97 supercharged pump... and that is DIRT cheap for a whole module!

Attention super sleuths and troubleshooters: I've got a random stall problem with my Riv; it's been creeping up on me for while, has me stumped. Here are the specs on the car:

• current mods are in sig
• 220k original miles
• original crank & cam position sensors
• original fuel pump
• fuel filter changed within last 5k miles
• no DTCs

Here are the symptoms:

• car stalls while driving, on decel only
• totally random, usually infrequent
• seemingly more frequent in warmer weather
• not related to moisture
• usually will restart while coasting
• sometimes will not start after stall

Background:

The first sign of trouble was on Aug 21, 2010, in the morning after a 1 hr (50 mile) drive on back roads. The engine didn't stall out that time. I arrived and parked as usual, then realized I needed to move the car about 2 mins later. Wouldn't start. I waited about 1 min, the car hick-upped and started right up. On the way back, the car stalled while driving about 1/2 way. In neutral, I was able to restart and continue. this happened 3-4 more times on the way home. One of those times I had to pull over and wait a couple mins before it would restart. I noticed as long as I kept gas applied, it would not stall - only while coasting or decelerating would it happen. And it was still random, not happening the majority of the time, only a few times.

Next day the car started okay and I drove for a couple weeks until it stalled one more time in early September. I restarted while rolling and had no more issues.

A few more weeks passed without problem. At the end of November I was pulling a tree home on the trailer and it stalled once again. Started right up again. About a week after that it stalled before the car was warmed up, started up again no problem.

I had no stalls all through December, January, and most of February. During this time time the temp was usually between 10-35ºF. It happened for the first time this year near the end of Feb. Again, started up while rolling. This month it happened more 3 times until yesterday, when it stalled in the morning on the way to work. This had never happened before. I noted it was unusually warm yesterday, at about 62ºF.

When it happened, I immediately shifted into neutral, waited for RPM to drop, then tried to crank. No start, tried again, no start, so I pulled over. I sat there for over 45 mins trying to start the car. I tried with gas pedal, without pedal, pumping gas, nothing worked. I waited 1, 2, 3, and 10 minutes between starts - no start (btw, the Red Top is one serious battery, and the OEM starter was amazingly durable). I must have turned the key 20-30 times.

I left the Riv and went to work for 12 hours. Called AAA and before loading the car I tried to start one last time. No start. Towed the car to local Buick dealership for diagnostic first thing this morning.

They called me around noon and reported the following:

• tech tried to start car in the morning. Would not start.
• pushed the car into the garage and tested fuel pressure - zero fuel pressure at rail.
• scanner showed no DTCs.
• cranked car again and started right up.
• drove car, shut off engine, started engine, no problems.
• techs cannot recreate the stall or the no start problem.
• except for the fuel pressure clue, they have no idea what is causing it.

At this point, I think replacing the original fuel pump would be a good investment at 220k miles, even if it's not the problem. The pump makes a normal (almost inaudible) noise when running.

I plan to replace the camshaft position sensor when I do the timing chain in the next few weeks. I wished I'd done this last year but didn't find the time.

Anyone think they know what's causing the problem?

I'll comment on this when I get home..................

AA, I have the exact same problem it sounds like. I started having the problem a couple years ago while I was having other problems so it was impossible to say exactly what was causing what but at this point I've replaced just about everything under the hood that's electrical-related. Basically, my engine will just die but not necessarily while decelerating I don't think. Most of the time I can fire it right back up while coasting. There is never any recovering it while it's dieing. Sometimes it takes a bit longer - 10 to 15 very long seconds I guess on occasion, before it starts back up. I haven't had to pull over yet though. I think it's the same for me where it's not happening during the winter months really. I have changed everything I can think of short of the PCM its self and I think the cam position sensor is original. I've changed my fuel pump and whatnot but I don't have any way to look at if I'm loosing fuel pressure while its actually happening due to wiring or something. I'm going to try to hold out on this until I can really examine the fuel pump wiring while I do a rewire/voltage booster install hopefully this summer.

Thanks for sharing. I would be more inclined to believe this is a fuel delivery problem if it ever happened while on the gas, but it has never cut out while accelerating. When it happens, I'm usually unaware, so I discover the stall either from the loss of power steering, the dash lights coming on, or hitting the gas and getting no power.

But the zero pressure reading at the rail seems like a nice clue. That could only be caused by the pump cutting out, right? Maybe it's a pump wiring issue?

Next time I stall and can't start, I will have my fuel pressure meter in the car to take a reading.

AA wrote:

Next time I stall and can't start, I will have my fuel pressure meter in the car to take a reading.

Actually, you're better off hooking up the gauge and taping it high on the windshield until it happens again. This way, you can watch the gauge to see if the pressure drops off, or if you simply lost it all because you were cranking it 50 times to try and get it started. Either the FP isn't getting power, or it's freezing up on you. Also, if and when the car stalls again, you can see the FP prime itself when you try to restart.....this will lead you in the proper direction as far as a repair.....

Another thing to hook up and put somewhere in view is a test light. Wire the test light to the FP relay under the backseat. It will (obviously) stay illuminated when the car is operating properly, and will go out if the FP loses power. It'll take some smart engineering on your part (which shouldn't be a problem), but having both of these (pressure gauge and test light) hooked up simultaneously will eventually lead you towards the proper repair. This way, you kill 2 dealer mechanics with one Riviera (haha).

I honestly have no clue why the dealer would give the car back to you without somewhat of an answer. Personally, I think it's bullshit. It didn't have any fuel pressure......obviously there's a f-in problem. I hate "prima donna" mechanics....lazy bastards.

When my fuel pump went, it did exactly what your car did. Mine stalled a couple of times in December, then again in March and finally quit in May. On the day it quit, it stalled four times heading home and I was able to re-start it each time until it finally left me at the side of the road. I also drained the battery dead trying to re-start at that point. Had it towed to a dealer, where they replaced the FP and have had no problems since.


On a side note: I am trying to solve a problem on my Dads car and have been doing some reading, and have found that sometimes a bad EGR valve can stall a car under deceleration. I ain't no mechanic so take that one for what its worth.

Good points. I like the test light idea, and I would have taped the gauge up earlier, but the stalling hasn't been happening frequently enough, and I really don't like driving around with the gauge there for weeks at a time. I drove the car home tonight - 30 miles - drove like a dream, no issues. I even stomped it from 65-90mph and no complaints.

The test light - I may try that. Then at least I would know if it's getting power or not. The idea that the fuel pump might be 'sticking', that makes some pretty good sense. I'd think the pump would most likely want to stick during idle (decel), or during starting, when less pressure is demanded. It never stalls during acceleration, and WOT it performs great. In hindsight, I may have ignored the pump as a possibility because it performs so well under these conditions. Question: when a pump sticks, does the sound change? Wouldn't it burn up in short time?

Thanks for the info, BMD. It's reassuring to hear a story that so closely parallels mine. I'm thinking I should just replace the pump. With so many miles, it's lived one hell of a life. If I do, I know exactly what kind I'll be replacing it with.

Oh, about the dealership - I really don't mind that they didn't solve the issue. They scanned for codes, test drove the car, and revealed a clue about the fuel pressure - at no cost to me.