libolt

I recently bought new fuel injectors from Southbay along with their adjustable fuel pressure regulator. I have the injectors installed into the fuel rail. I have also installed a new diaphragm. However, while the fuel rail is attached to the fuel lines it is sitting free in the engine bay since I was checking for leaks. The injectors are Not pressed into the intake. I hooked up a fuel pressure gauge to dial the pressure in. The first couple of times I turned the key the pressure shot up and then took a while to bleed off. Since then the gauge shows it shoot up as the fuel pump primes then quickly drops below 20 psi when the fuel pump shuts off and goes to 0 in seconds.

So I reinstalled the stock FPR and when I turn the key it pressurizes to 43.5 then quickly drops just like the southbay AFPR.

I have checked everything for visible signs of leaks and can't find any. I replaced the o-rings on each side of both metal fuel lines that plug into the rail since some of them were bad.

Also the fuel pump was replaced about 2 years and only 1000 or so miles ago with an AC Delco unit.

What should I do/check next?

vetteoz

iTrader: (13)

If not leaking past reg to return line, then pressure has to be bleeding back to the tank ; bad check valve on supply line?
Do the clamp test;
hot wire ( 12V to terminal G of ALDL ) the pump to run for more than 2 sec,
build rail pressure then clamp the supply line shut and turn pump off to see if pressure holds
Can do the same test on the return line just to confirm both regs are not leaking ( unlikely )

libolt

I haven't had a chance to test the above yet. However, I did clamp the return line and then turned the key to on. The fuel pressure shot up to over 70 PSI and very very slowly began to drop. This is with the stock FPR.

libolt

Yesterday I took the fuel rail back out of the car and disassembled everything. I looked over the new regulator diaphragm and didnt find any signs of damage. I removed all of the injectors and inspected their o-rings which seem to be fine. Then i used brake cleaner to clear some gunk out of each injector slot. I then reassembled everything, lubing the o-rings as i went. I tightened down the stock fuel pressure regulator as tight as I was able to.

The first time I turned the key to on the fuel pressure shot up to between 35 and 38 psi before very slowly bleeding off. The second time it shot up over 40 and bled off somewhat quicker. After that it would go over 40 each time the pump primed and drop more rapidly.

I couldnt find any visible signs of leaks. However, I'm wondering if something is going on with the injectors. They're the yellow top Ford/Bosch II injectors. I installed clips on each injector. Half of the clips are new as I broke some removing the old ones. What i have noticed is that I am able to wiggle the injectors back and forth a bit in the fuel rail. Could this be a problem? I tried to push each injector in solidly before rotating the clips into the locked position

libolt

I have now replaced some o-rings on the fuel/return lines that tore, lubed them and reconnected everything after reinstalling the fuel rail into the manifold and am still losing pressure rapidly. The injectors seem to be pretty tight though they can rotate side to side a bit.

Any help is greatly appreciated.

RED86Z28

My car rapidly drops fuel pressure when the pump turns off and has for the past 7 years. I drive it every day without issue.

libolt

Ok I guess I will put everything back together this weekend and see what the pressure is like with the engine running.

85-87IROC-LB9s

iTrader: (1)

To: libolt,

I two have encountered this problem, and I'm finally think I may have found the problem. I too have done all the same like you did, new fuel pump, regulator, and Ford yellow top Bosch II's. To no avail, the pressure still seemed to drop rapidly, and was started to get a little worried. What I found out is the mainline fuel feed line coming out of the tank, which goes from a rubber flex line and then transitions into the 3/8 hardline going towards the fuel filter is leaking vapor. It is leaking right at the transition from the rubber to steel hardline crimp. I confirmed this because one time as I was working underneath the car I saw fuel running down that line, but very slowly and not leaking quickly. Overtime the liquid fuel started to turn into vapor as I could see residue around the leaking area and not liquid fuel itself. This along with all o-rings in the main fuel feed line which have deterioted, is contributing to a rapid fuel pressure drop, which gives the car a very hard starting. It's a very rare and tricky problem, as my 1985 IROC, which is all original does not have this problem, even when it was left abandoned for 10 years. What I'm going to do is replace all o-rings throughout the main fuel feed line and return line, and make a new AN line towards the filter, along with using the required vition o-rings. I found out very early the regular rubber o-rings I was putting were deteriorating rapidly. When I finish this work I'll try and confirm to you wether or not this has solved the problem, which has been plaqueing me for nearly 5 years. If it doesn't then I don"t know what will. Sorry if this long. Hope this helps, if you haven't cured the problem.

Jersey89GTA

iTrader: (1)

Silly thought but what about the gas cap ? is it holding pressure.

Wierd thing with my car is it runs great with a full tank of fuel. Gets down to a 1/4, runs like a grizzly bear under the hood, I fill it, smooths out-

Would you think FPR ?

ASE doc

You were on the right track with the fuel line pinch off tests. These tests, when done correctly, are a fool proof diagnostic of the system. It is fairly common for the rubber section in the tank to fail and cause pressure to drop quickly as the fuel leaks back into the tank. It is also somewhat common for the regulator not to hold pressure as it should, due to a damaged or misaligned seat. Using the pinch off pliers, pinch off the return line, as you did, and note how long pressure holds after the pump stops running. If pressure holds much longer than with the line unpinched, you have a regulator issue. Not with the diaphram, but with the seat. Check it out and see what's wrong there.

Leaking injectors are not common, but they do happen. To test for these, run the pump and while the pump is running, pinch off the return and supply line at the same time, then stop the pump right away(don't want to dead head the pump for more than several seconds). Now watch pressure. If it drops more than 10 psi in 1 minute. You have an injector leak that needs attention. Repeat the test to verify that fuel is not leaking past the pinch off pliers.

To test for a leak in the tank or a failed check valve at the pump, follow the test detailed by vetteoz. Just be sure to pinch the supply line before the pump stops running so that you trap pressure in the rails. If pressure holds in this state, you have a leak in the tank.