Good day to one and all, hoping all is well in these times. I am now more confused with an issue I had accepted for the past 5 yrs, something I could not figure out, until I got tired of being tired.
Realizing how much I appreciate my 91 truck 2 wheel drive. The issue has been an cold starting issue, which I have seen many topics on this site, at the same time have posted likewise on this issue.
I decided to dig deeper, desperate to where I went to toyota dealership for a diagnosis that cost me $180.00. First, I want to say thanks in advance for all and any help. These are some few things I
have tested and changed before going to toyota. Start injector time switch, Water temp sensor and cold start injector. My 1st diagnosis from toyota was the fuel pressure regulator. I replaced it on my
own, but the problem still persist, after returning to them with the issue, they rechecked it and said, "vacuum hoses from fuel pressure regulator and EGR are routed wrong, rerouted vacuum hoses and
now fuel pressure regulator is getting needed to operate. I thought the problem was fixed, I was wrong. I return the following day with same complaint. Toyota looked at it, their diagnosis, with video "tested
fuel pressure at idle is 34psi, when vehicle is shut off it loses all fuel pressure, it should hold at least 5psi bellow running pressure". I understood that by watching the video. They waned $1600 to replace
fuel pump, bracket and everything else that was connected to the pump itself. That kind of money is not easy to come by around this time. I dropped the tank and replaced the fuel pump.
AS of today, I used the fuel injector pressure tester to test the fuel pressure, with the the ignition switch on, engine off as per manual it read 38 to 44 psi, as soon as I turn the ignition to the off position, it dropped
all pressure to 0 within seconds .I tried it the second time but this time their was a sound that came somewhere from the intake manifold, can't pinpoint exactly where, but again it lost all pressure. I tried to get a 2nd
and 3rd reading but this time it held the required psi between 38 to 44psi.I believe the tech at toyota did not experience this. The second test I did was with the engine in idle. With the vacuum sensing hose detached
my reading was 38 to 44 psi, with the vacuum sensing attached it read 33 to 37psi, both were between specs.
My question is why is the psi fluctuating and not holding the pressure? what would cause it. I believe the tech did not experience the steady holding of the psi, only the dropping of it why he recommended a new fuel pump. Or is the fuel pump
I replaced is a defect. Can someone help me? Thanks

 

The spec for "holding" pressure is "stay above 21 psi for 5 minutes." http://web.archive.org/web/201003261...87fuelpump.pdf (I have no idea where you got "should hold at least 5psi below running pressure.") If it doesn't hold pressure, there's only a few places for it to go. I assume you're not sitting in a puddle of gasoline. Your mechanic (and you) must have thought it was the check valve in the fuel pump, so you replaced the pump. Sorry to tell you this, but that was a waste of money/time. A perfectly tuned pickup will back-flow into the tank all the way to zero overnight, and yet we expect the truck to start right up. It's not a cause of cold stating problems.

Where else could the fuel go? It could leak through the FPR to the return line, but again, that's not a cause of hard-starting as long as the pump and FPR can reach the required running pressure (you tested that). It could leak through the FPR vacuum line, which is a problem because you will run so rich it might not start at all. Unlikely (with a new FPR), but easy to check: pull off the vacuum line and see if gasoline pours out.

So that brings us to the injectors. If an injector is sticking open, the fuel will drain out there. That rich cylinder will make it hard to start. You might even have an injector that sticks open only "some" of the time. You can try to check this by removing the plenum (upper intake manifold), sliding a slip of paper down each intake runner so the end sits under the injector, then pressurize the rail with the jumper (you'll need to run the return line to a suitable container, or use a long line to re-connect it to the return hard-line). Does one of the paper slips get wet at the end?

 

Good Morning Scope 103,

I look forward to removing the upper intake manifold as of getting off work today. Thanks
I will keep you posted

 

Scoop103, I ran the 1st test and all 3 slips were wet. I ran it twice more and they were all dry.
ran the test this morning 1 was wet. Should I change the ones that got wet? Thanks

 

Whatever you decide to do I would do it to all of the injectors. You can send them off to be cleaned, or replace the entire set. I had the same issue with fuel pressure dissipating right after shut off and sure enough more than half of my injectors were leaking.

If you end up replacing injectors I would recommend sticking with OEM "rebuilt" injectors. I had some aftermarket ones I tried and the tips ended up melting and that's what caused that leaking issue on mine.

I said rebuilt with quotations because all rebuilt Injectors are is new seals, new filter basket, and cleaned with the solenoid tested. I got my set of 6 OEM rebuilt injectors on ebay for $80

 

After removing ,I will test, clean then rebuild them, thanks
when done I will post to share how things went.

 

Greetings to one and all, hoping all is well in these times. I cleaned and tested the fuel injectors, replaced them all,
but did not fix the initial problem. After putting a 100,000 miles since since purchase in 2014,I'm glad I did. Problem
of starting issue continues. Thanks