i just replaced my engine with one that i was told came out of a 90,000 mile sonoma 98 that was wrecked. i had good fuel pressure readings before. ive been messing with the timing and figured id check the fuel pressure.. key on we got like 62 ish once pump shuts off it drops like a rock down to like 30 . the return line could move up and down a bit so i tweaked it and it will stay down on its own now but no change in the fuel pressures and didnt see anything leaking. cranking i got like 35 psi.. wondering if i have a bad fuel pressure regulator or if the return line could be causing probs. one other thing a few time after i was done cranking it sounded like somthing was rattling inside the intake.. thanks.

 

im sorry i ment a fuel pressure regulator.

 

No, a loose or leaking return line would not cause the pressure to leak down.

What did you mistakenly say instead of fuel pressure regulator in your first post? Could you edit it to say what you meant to say originally? It is a bit confusing...

 

i said fuel injector, so i should prbly just replace the regulator huh

 

Definitely sounds like a bad FPR.

 

i replaced the regulator today. also relized i had the fuel line hold down backwards so i fixed that and before i bolted everything back down i hooked up fuel system and checked it and same problem. i undid all the injectors one had a broken ear. and tried to see if i could see any leaking but couldnt. would i even be able to see that? i guess one alternative would be i could swap out the whole spyder off the old motor and see. what do you think?

 

If you cannot see a leak at the spider, then the only other possibilities are external fuel line leaks (easy to see) or a problem in the tank.

 

i got all my timing figured out.. the fuel pressure bounces around from 50-55 while cranking but drops as soon as the pump turns off.. i tried using my fuel system canister but it dosent help. it had new gas in it and i seen where some of the old gas got in it and was settling to the bootom a dark orange..it will start on brake clean but as soon as it burns it up it usually dies. it did run for a min or so shaking and running terrible.. so what should i do now? obvisley it seems to be fuel related.. the injectors are firing. should id rop the tank and dump the gas and put in a new fuel pump?

 

also wondering 98 kinda seems like it used to diffrent parts? one for a plastic tank and one for a steel tank?

 

Sounds like the check valve or the flex line in the fuel pump is leaking. The only way to tell for sure is isolate the fuel pump from the injectors after it pressureizes the system. If pressure holds, the problem is in the tank.

2 door uses a steel tank aft axle. 4 door uses a plastic tank midship.