FAQ: Fuel Pump - General Questions, Compatibility & Troubleshooting

Ok I've got it figured out. I was testing the wrong wire on the pigtail. I realize now the gray wire is the power wire. The wire receives battery voltage for the pump cycle and mid 11's when being cranked over. I tested the ground, it is good. So I smacked the pump lightly with a rubber hammer and the car fired right up then stalled out a min later. Smacked the pump again car fired then stalled 10 seconds later. Obviously its a bad pump. Thanks for the help.

cjoform wrote:

Ok I've got it figured out. I was testing the wrong wire on the pigtail. I realize now the gray wire is the power wire. The wire receives battery voltage for the pump cycle and mid 11's when being cranked over. I tested the ground, it is good. So I smacked the pump lightly with a rubber hammer and the car fired right up then stalled out a min later. Smacked the pump again car fired then stalled 10 seconds later. Obviously its a bad pump. Thanks for the help.

glad you found the problem.

Dealer (or anyone with the Tech II tool) can "command" the pump on - if it's failed then it won't command on. Hopefully nothing else is wrong - for engineering reasons the long-lifetime components in teh Riv tend to fail in groups.

Albertj

Thanks for the advice albertj. When I get the cash saved up I will buy a pump and see what happens. If there are more problems then I guess this car aint for me and I should go back to my old stuff haha. Anyway when I get a pump and put it in I'll let everyone know the results.

http://www.zzperformance.com/grand_prix/products1.php?id=573&catid=113
I bought this fuel pump since mine died on me last night

Travis dos your pump have the small tube on the top tho?
if not then you should mod your fuel 'bucket' add a bigger ventile on the bottom of it.

i installed in my car one what looked the same but it did not have the small tube on top. in the bucket are 2 ventiles on the bottom. one works freely by itself. other works whit the pump....pump sucks fuel into the bucket. my car worked fine when the tank was full or half full. if it was under half and on driving 70miph or faster the car started to 'jump'. the pump did not get enaf fuel cos the bucket had no other way the the small ventile to fill it up. so alot of air cone to the pump.
my pump died after 400miles...now i got the original one whti the small tube and everythign works fine again.

In case anybody is following this I replaced the fuel pump and fuel filter 2 days ago. So far no problems in the 100 miles that I have driven it. Thanks for the help.

Good to hear . Don't you love it when everything starts working again??

Congrats on the fix!

AHEM... Travis, how did the universal pump job go?

Eldo wrote:

AHEM... Travis, how did the universal pump job go?

Baller... It's quiet though.. i don't like that.. I would rather it be screaming..

Had to fab my own Venturi setup. Let me just say i hope quicksteel is E85 safe

BTW that Aurora Fuel level sensor WORKS

The company is from canada.. they shipped hella fast too

I didn't even notice the 'venturi' pump when I had my fuel pump assy out to fix the sender... Is it a separate electric pump? And why doesn't the L36 have one?

It's not an electric pump, It's a jet pump. Uses venturi effect to keep the plastic can full of fuel at all times so as not to cavitate the electric pump.

Rickw wrote:

It's not an electric pump, It's a jet pump. Uses venturi effect to keep the plastic can full of fuel at all times so as not to cavitate the electric pump.

I still don't quite understand... Does it just split some gas off of the main pump flow? And again, why would the N/A cars not have it?

Eldo wrote:

Rickw wrote:

It's not an electric pump, It's a jet pump. Uses venturi effect to keep the plastic can full of fuel at all times so as not to cavitate the electric pump.

I still don't quite understand... Does it just split some gas off of the main pump flow? And again, why would the N/A cars not have it?

To answer the first question, sort of but not really. The venturi feed uses the pressure that the pump itsself makes but other than that, it works independantly. It suctions and displaces its fuel seperately from the pump supply for the motor. It couldn't just split some gas off the main pump because then it wouldn't be able to retain fuel pressure. (This is exactly what happens when you rig up a walbro pump - fuel pressure bleeds off)

Second question I can only offer speculation. Traditionally, fuel pumps didn't have anything like this. The tanks just had baffles to help control sloshing of the gas which can starve the fuel pump if fuel level isn't very high. I believe the high performance cars started using the more complex venturi feed pumps and other various solutions to keep ample fuel for the pump during cornering and such. Our cars, having supercahrged 3.8L in them happen to have some pretty high output fuel pumps stock. The fuel pumps that come in L67 powered cars are higher flowing than the pumps in most V8's in its time. GM didn't think the L36 non-supercharged needed the assurance of a constant venturi-feed fuel supply.

http://en.wikipedia.org/wiki/Eductor-jet_pump
This design has been used in Aviation for a long time.
It's free fuel pressure sort of. But necessary to keep the supply of fuel available during maneuvers.

Rickw wrote:

http://en.wikipedia.org/wiki/Eductor-jet_pump

This is a pretty neat concept - basically using fluid pressure to create fluid suction.

Link

That link does a pretty good job of explaining how the venturi works in our pumps as well as how it works with the fuel bucket and tank.

For the record.. When friends follow you for periods of time.. Their eyes burn.. WHEN your running E85......

THUS E85 FTW. (period)

Thanks for that Racetronix link, Codith. It seems that the General really did design this setup for 10/10 circumstances...

They are splitting off some of the pump output to run the jet pump, but that gains them about twice as much total fuel into the bucket. I would have thought that just the bleed from the pump output and the fuel from the return line would be enough... But, I guess they found that you could still run dry if you were lapping Daytona with a nearly empty tank.

Anyone know why this 97 L67 pump would not work in my 98?

What did the P/N research show as far as compatibility between the two, SC and non-SC.???
There is also a topic in here somewhere where someone successfully installed the sending unit made for another car into theirs.
I thought you were following that one at the time, I don't remember. Do a search for it if you haven't already.

Rickw wrote:

What did the P/N research show as far as compatibility between the two, SC and non-SC.???
There is also a topic in here somewhere where someone successfully installed the sending unit made for another car into theirs.

Yes, some folks have successfully used other senders... I agree that they ought to be the same, but then again, I wouldn't have designed 2 such wildly different fuel modules.

My research for my '97 shows different Delco numbers for the different senders for the MU33/NA and MU35/SC modules. The eBay seller I'm dealing with has more than one brand, and while I BID on the MU33 sender, he said he is sending me one that will fit the MU35...

I'll get a new O-ring before I go in, and if something is wrong with the new sender, I'll just re-tension the brushes in my old one again... I also have a used sender off of a Chevy S-10 fuel module, and I'm going to see how the resistance of the circuit boards compares.

I saw this guys auction and was interested in a replacement as I had cobbled the wrong pump in my car and was having trouble.

Having a 98 I asked this guy if his kit would work, he said yes, at that point I was reading every word in his auction and saw where he listed all the "MU" numbers that the pump fit and discovered I already had in stock a new complete delco module he listed (fit a 99 tahoe).

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=360227353710&viewitem=&sspagename=STRK%3AMEWAX%3AIT

I ripped into my tank and pulled out the cobbled unit and rebuilt my entire module using the lower 50% of the Tahoe unit, the only trouble I had was getting the high pressure nylon line on and off .

That was yesterday, what a difference, works perfectly.
The new leftover level sensor board and brushes looked the same but the float rod was different.

Did anyone know Bosch made Fuel Pumps for our cars.? Wondering if they are any better than the Chinese made AC Delco knock-offs.