88' FJ62 having hot start problems even worse after new FPR...

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May 19, 2012
Colorado Springs, CO
Long time lurker, first time posting. My 1988 FJ62, with 213K, is having a rough time hot starting, even after I had the FPR replaced. It's my DD, though I usually have a work car to drive during business hours.

New TPS, FPR, tuneup, alternator. I have not done or even tested the fuel pump(happening this morning) or the fuel pulsation dampener(though I do tighten the screw under the cap;)).

My inexperienced mechanic's mind is leaning toward fuel pump after reading about thirty threads on here, but I'd appreciate any and all help. I'm doing the work myself and have an FSM and a few weeks on my hands. Seems like every time I take it to a mechanic I get poor results, I'd rather research it here and do it myself or at least diagnose it with the help of Ih8mud.com.

Also, I have not checked these things, but will after the fuel pump; vacuum tubing, timing, injectors(though I do run BG44K through regularly).

Check the relevant water temperature sensors. There are specs for each in the FSM. You need to check the EFI water temperature sensor (182-65 in image below), the water temp switch (182-67) and the cold start timer switch (182-66). It's not all that easy to get to these, so I would do them in that order.

I read a thread speaking about checking them yesterday. You are right, they do not look easy to get to, but I'll give them a look.

Thanks for the advice.
Yeah, I always bang up my knuckles pretty good getting to those sensors. Still, rather then continuing to throw parts at the problem I think more diagnosis is warranted. Did you test fuel pump pressure yet? I built a simple jig that I could bolt to the banjo fitting on the supply line running to the cold start valve. That way you can see if something wonky is going on with fuel supply to the motor when it's warm.
Is there a poor man's way of testing the fuel pressure, as I don't have the right tools for it? I'm going to venture out in the snow(17F today:confused:) in a bit and continue testing the sensors you mentioned and the fuel pump.

Well you'll need a pressure gauge for sure. Spec for fuel rail pressure is 37-46psi, so a gauge that can measure in that range is needed. I got mine at a hardware store. It's intended for measuring water pressure but works fine for this application. The challenge is to connect it to the fuel rail via fittings and a hose in a manner that doesn't leak. (Obviously the exhaust manifold is right below the fuel rail and you sure don't want fuel dripping onto a hot exhaust.) Toyota has an SST for this purpose, but you'll need to build your own. I found the pipe that runs between the fuel rail and the cold start valve at a junkyard and paid something like $4 for it. Then I cut it in half and attached a piece of fuel line using a miniature hose clamp to the end, then ran that to a brass fitting attached to the pressure gauge. Then I temporarily removed the OEM pipe to the cold start valve and bolted my adapter to the fuel rail. Of course the cold start valve was nonoperational during my testing, but this was during the summer and I didn't really need it. 17* F in the winter is another matter though. And you'd want to measure pressure both with a cold and a hot engine to make sure nothing strange is going on.
I can't even get it to idle now, so no chance of even getting a hot engine, as soon as the choke comes off(automatically), it wants to die unless I give it gas or use the hand throttle. Even then it sounds really weak and rough, as well as it fluctuating. If it were a Harley it would probably be tuned, but it sounds like it wants to die when I give it any gas and there's some hesitation.

I'm going to go out after a bit and retest the ECU and all the sensors again. It's had a recent tune-up, so it's possibly the dampener or ECU itself, but that's my inexperienced opinion. I checked the fuel tank it's spotless. It was running way better before the FPR was replaced. At least then it was just having warm start problems.

Someone mentioned a ground in the left quarter panel being and issue or at the ECU, any thoughts on that?

I'm from San Diego originally, so I doubt I'll be tearing too much apart in this weather. I did the thermostat in 10 degree weather a few years ago so I've learned my lesson.

Thanks again.
It's very unlikely to be a bad ECU. Those things are very robust and of the many, many threads were someone said "it must be a bad ECU" all but maybe one or two were wrong.

Just a thought here: when you did your tuneup did you disconnect the VAF? And if you did, you did not, I hope, remove the two screws that hold the black connector to the VAF and then tug on the connector. Doing so is a common mistake and tears off some little metal tabs from a printed circuit board inside the VAF. This wreaks havoc and either takes some skilled soldering or a replacement VAF to fix.
I did not do the tune-up myself the last time, but the mechanic that did it it pretty reliable for non-diagnostic issues. Although he has thrown non OEM parts on my truck, Denso, but still not the right part for my truck, before.

I checked through almost everything that I could the other day and this is what I found. The distributor is out of spec, 150 Ohms rather than the 185-230~(I don't have my FSM in front of me right now). It was both the N and G connectors that tested out of spec.

I still need to double check that my ECU has a proper ground, physically. The truck is starting but not idling. I pulled the Cold Start Injector cable and the truck wouldn't even start, so I'm wondering if it's a fuel pump problem now.

Thanks in advance for any help.

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