Quick question,

We are checking the fuel pressure on my buddies 1989 Trans am. We get 44 while its on the start position but then you hear the relay click and automatically drops back to 0 psi.


Is the relay the culprit?

 

Does the pump prime when you turn the key on?

 

Yes it does.

 

Aight let me be more specific to get some more help.

We have the FP gauge hooked up, you put the key onto the start position and the pump primes and is around at 43-45 PSI but then you hear the relay click and right when it does so the fuel pressure drops to around 3-6 Psi and drops off right away to 0. I was trying to see if the fuel pressure regulator was leaking and unhooked the return line and wanted to see how much fuel was being returned. It was not much but it would return the same amount every time when priming and of course stop when its not.

As for the car starting, it wont start at all, I figured if it was flooding the engine, it would atleast start for a few seconds, it wont. When cranking it and giving it gas when it has fuel pressure, it will only stay on with some gas and the FP would stay on at around 35-40 psi before stalling.


We also tried seeing if it was getting constant 12v at the relay and we did get 11~ volts but could not get it to read it again and had problems but the thing was that the cables were not fully seated in the connector and had some exposed wires on the back of the connector. So we plan to fix that as well.


My Question is basically, even after you hear the relay click off or click in general after it primes, it should not auto drop fuel pressure right? What can cause this? Weak fuel pump? Fuel filter? or maybe the rubber hose inside the tank?

 

The pressure should not drop. The most common cause of this is leaky injectors.

 

Probably leaky injectors, or some other fuel leak.

Try starting with the pedal all the way to the floor.

 

try pulling your plugs, if you have a wet cylinder you have a leaky injector

 

if you find its not the injectors... (sorry to say) on to the ck valve at the pump... seems like a quick leakdown injectors.

 

Its not the injectors. No leaking from them at all.

We removed the fuel pressure regulator and found it to be bare without any orings. Would that cause this? We got a pack of rubber O-rings but have no idea how they go. Any help here? Diagrams or picture install would be nice.

 

HA, someone took it apart and had leftover parts.....

OR they were cheap material and dissolved.

 

So where do the rubber O-Rings go? Any diagrams or help would be nice.

It came with a pack of O-Rings that come with about 8-10 and they seem to be in pairs in sizes.

 

O rings are for fuel rail if you take it apart. If you are just replacing the diaphram in the pressure regulator, you won't need them.

 

I figured and thats what I told my friend but since the PO was a total screw up, we figured he did something wrong.

So its just a simple replace the regulator similar to my TBI.


So what would be next to check? Its still dropping pressure last time we worked on it. It would climb to 45 while it primes then once it stops it drops to 10~ and keep dropping slowly until it goes to 0 in a matter of 3-5 seconds.

What can it be? Right now I am thinking:

1.Replace Relay
2.Replace Fuel Filter
3.Drop the tank and have a look.


I feel number 3 is what is gonna be needed since if what Esei says is true, then its a in tank issue but then again if the relay is closing to let the pump prime, then its working fine, no? As for the Fuel filter, its not seated right and has been scrapped a few times since its the lowest part of the car right now but I am 99.9% sure its probably not gonna cause this.

I really want to drop the tank not just because of this, just due to the fact that the Fuel gauge is not working. That alone should of been enough reason to drop the tank a while ago and have a look. Hopefully my friend puts some time out this weekend to have the option available to drop the tank if needed. Doubt it though. Last time I heard they charge $350-$600 to do the job at a local shop.