Troubleshoot bad fuel pump
Thread Starter
Joined: Mar 2006
Posts: 4,668
Likes: 5
From: Central Kentucky
Troubleshoot bad fuel pump Engine was running like crap so I naturally blamed the opti. Hey that worked nearly every time in the past. 
But it appears that the fuel delivery may be bad. So I need to know the proper way to troubleshoot the fuel system so I can ensure I get the faulty component this time.
When I turn the key. I think I am hearing something from the back of the car but I cant tell if its a "normal" sound. Also if I hook a fuel pressure gauge to the fuel rail and turn the key, the gauge is not showing pressure. If I remove the gauge and manually press the schrader valve, I get a small spritz of fuel but nothing to speak of.
Does this sound like a fuel pump? Could it be anything else in the fuel system? I dont want to go after the pump if there is anything else it could possibly be.
Thanks.
But it appears that the fuel delivery may be bad. So I need to know the proper way to troubleshoot the fuel system so I can ensure I get the faulty component this time.
When I turn the key. I think I am hearing something from the back of the car but I cant tell if its a "normal" sound. Also if I hook a fuel pressure gauge to the fuel rail and turn the key, the gauge is not showing pressure. If I remove the gauge and manually press the schrader valve, I get a small spritz of fuel but nothing to speak of.
Does this sound like a fuel pump? Could it be anything else in the fuel system? I dont want to go after the pump if there is anything else it could possibly be.
Thanks.
TECH Veteran
Joined: Apr 2008
Posts: 4,985
Likes: 112
if the FP gauge shows no PSI...pump is bad
just a few PSI is enough for gas to come out the schrader valve...but no where near enough to start it
get a BFH and wack the bottom of fuel tank where pump is. This "sometimes" wakes it up. Not always but if it did it would be another sign the pump is...intermittent at best
still if FP gauge shows zero...that is enough to show pump is not working itself or the wiring to it has been compromised
just a few PSI is enough for gas to come out the schrader valve...but no where near enough to start it
get a BFH and wack the bottom of fuel tank where pump is. This "sometimes" wakes it up. Not always but if it did it would be another sign the pump is...intermittent at best
still if FP gauge shows zero...that is enough to show pump is not working itself or the wiring to it has been compromised
Thread Starter
Joined: Mar 2006
Posts: 4,668
Likes: 5
From: Central Kentucky
Got it.
So I will be dropping the tank to do even though its more PITA. I just cant bring myself to do the access panel above the tank.
That said, can the rear end just be lowered to the floor or does it need to be completely removed from under the car?
So I will be dropping the tank to do even though its more PITA. I just cant bring myself to do the access panel above the tank.
That said, can the rear end just be lowered to the floor or does it need to be completely removed from under the car?
Since you have a convertible it makes sense to drop the tank to replace the fuel pump since you don't have quite the space to cut an access panel. I think you have to remove the rear end to get the tank out.
TECH Resident
Joined: Jun 2002
Posts: 943
Likes: 2
From: Houston
You dont have to remove the rear end to get the tank out. Disconnect the LCA's, the panhard rod, and slowly lift the rear body of the car. Keep the rear end connected to the driveshaft and just lift the car. That will give you enough room to get the tank out.
Words of caution, be careful of the brake lines being stretched. If I remember correctly, there is an attachment point on the body in the rear axle cavity where you can disconnect the lines from the body and get the extra length needed.
Words of caution, be careful of the brake lines being stretched. If I remember correctly, there is an attachment point on the body in the rear axle cavity where you can disconnect the lines from the body and get the extra length needed.
TECH Veteran
Joined: Apr 2008
Posts: 4,985
Likes: 112
OP
while a tank drop and pump replacement is likely......you could swap the fuel filter first to see if that resolves your problem. You mention you hear the FP prime and if it is FP that needs replacing, you should do a new fuel filter anyway.
Best case you are back on the road for a few $ and WAY easier than dropping tank but if not you should replace fuel filter anyway
You will have to disconnect fuel lines and EVAP lines from tank before you slide it out
while a tank drop and pump replacement is likely......you could swap the fuel filter first to see if that resolves your problem. You mention you hear the FP prime and if it is FP that needs replacing, you should do a new fuel filter anyway.
Best case you are back on the road for a few $ and WAY easier than dropping tank but if not you should replace fuel filter anyway
You will have to disconnect fuel lines and EVAP lines from tank before you slide it out
You dont have to remove the rear end to get the tank out. Disconnect the LCA's, the panhard rod, and slowly lift the rear body of the car. Keep the rear end connected to the driveshaft and just lift the car. That will give you enough room to get the tank out.
Words of caution, be careful of the brake lines being stretched. If I remember correctly, there is an attachment point on the body in the rear axle cavity where you can disconnect the lines from the body and get the extra length needed.
Words of caution, be careful of the brake lines being stretched. If I remember correctly, there is an attachment point on the body in the rear axle cavity where you can disconnect the lines from the body and get the extra length needed.
The LCA's and torque arm (stock one anyway) do not have to come off. The panhard rod and brace come out, shocks unbolted and springs removed, as well as unbolting the sway bar end links. The brake line bracket attached to the body comes loose from the frame rail, so you do not have to break the rear brake lines. The exhaust has to drop and preferably come out, which should be possible with the rear end so low. It's still a PITA, and is made more difficult with any amount of fuel in there.
Make darn sure it's the pump, because it's going to take you at least a day to do it yourself. Check your PCM BATT fuse, as that powers the fuel pump.
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Verdad Gallardo TECH Resident
Joined: Jun 2002
Posts: 943
Likes: 2
From: Houston
Fuel Pump Prime Connector 
Within the wiring harness on the passenger side of the engine compartment is the fuel pump prime connector. With the engine off, hook up a 12v supply to it and the pump will power up. It's a good way to listen to the pump while the engine is off to mmake sure it's actually working. Check the fuel pressure while the pump is on.
Last edited by Gangly; Feb 28, 2017 at 01:18 PM. Reason: Photo
TECH Resident
Joined: Jun 2013
Posts: 853
Likes: 32
From: Kernersville, NC
A little gotcha to watch out for....
My fuel gauge is from autozone and it can be put on the fuel rail schrader valve and not read a thing. The center pin of that gauge doesn't stay centered and will slip to the side and not press in the scharader valve pin.
I'm not saying that is happening, but it's made me go wtf more than once.
My fuel gauge is from autozone and it can be put on the fuel rail schrader valve and not read a thing. The center pin of that gauge doesn't stay centered and will slip to the side and not press in the scharader valve pin.
I'm not saying that is happening, but it's made me go wtf more than once.
Thread Starter
Joined: Mar 2006
Posts: 4,668
Likes: 5
From: Central Kentucky
Turned out the fuel pump was good after all. I think I ran into a similar issue with the gauge not attaching properly and therefore giving a false reading.
Wohoo....but the car still aint running. It has a new opti so I wanna rule that out. All thats really left is plug wires, plugs, coil and ICM.
Wohoo....but the car still aint running. It has a new opti so I wanna rule that out. All thats really left is plug wires, plugs, coil and ICM.
2. What brand is the opti?
I ask because it's not completely unheard of that aftermarket/rebuilt optis come dead on arrival.
The best-bet replacement is a new AC-DELCO opti.
KW