One problem? Two problems? Where do I start.
 

Hi guys,

It's been awhile since I've been on this board. Shockingly, my 94 3.0, auto has been a pretty good vehicle for the last few months. It's getting ready for its 200k birthday in a few more weeks or 200k head gasket blow - time will tell. Unfortunately, it's reverting back to its old, problematic self.

I'm having an intermittent starting problem. I've searched around, but I'm only finding people with semi-similar problems.

What I do know:
1. It never acts up when cold.
2. It's hit or miss on hot starts. Sometimes it turns right over. Other times, it will crank like no tomorrow, but never go.
3. It has died while driving. No sputter, just engine off. Most of the time, it starts right back up if I throw it into neutral.
4. I had a friend sit and crank it when it pulled this in a parking lot the other day. The tail pipe didn't really smell like fuel. Should it? Also, it smelled very, very rich when it did finally start.
5. I can't remember how this coincides with the starting problem, but one day I went to fuel up and my gas cap didn't hiss at all. It always had before. Thought nothing of it at the time, and just bought a new cap. Still no hiss.
6. There is spark.
7. Also, if it matters, my truck got an extensive check and cleaning of the fuel lines and injectors a few months ago. Sort of a funny story. Started up one day with zero power and a shaky engine. I limped it over to the mechanic at 10 mph because I had no time for its shenanigans. Anyways, the mechanic spent two days thinking the entire fuel rail was clogged. KISS right? Darn thing skipped the timing belt and lost the passenger cylinder bank. He never thought to check the timing belt, because it was still in time according to the gun since that all runs off the driver's cam. Oops. To say the least, his boss was pissed. The 70 year old master, figured it out in about a half hour. Anyways, I'd have to highly doubt any sort of clogging or injector problem, since those were pulled, cleaned and tested :)

Anyways, I started thinking deeply about the gas cap thing and how weird it is that it would change sound so suddenly. And it has been hot, so I would think it should hiss right now.

So, is the gas cap related to the starting? I just need a starting point before I go barking up the wrong tree. I can replace parts all day long, but I've never been very good at identifying the problem.

No idea, but have you ruled out fuel pressure? Next time it fails, let it crank for a bit then crack the fuel line on the engine side of the filter. You should get a spray from residual fuel pressure, that'll rule out your pump or filter or a crack in the fuel line.

If it was a crack in the fuel line, you'd smell gas.
Doing the spray test on the fuel line is a good way to check the pump for correct pressure.
I was told that if you pull the vacuum hose off of the fuel pressure regulator, and there's gas there, replace it.
When's the last time you replaced the filter? They get clogged, and it's been 18 years since the truck was new.
I had a problem where mine (1990 V6 3.0 auto) was hellish to start cold, but did OK after it was warm. Then, it cut out while driving once, then again a couple weeks later, then would just start, run for like 3 seconds, then shut down. The problem ended up being the Circuit Opening Relay, Check that. I think the starter was at fault initially, because of the way I used to start it when it acted up. It wouldn't crank sometimes, so I would turn the key and release it rapidly until it turned over. I think this ended the starter, as well as the COR. The COR is like 2 relays. One side powers the pump during cranking, then after starting, the other side takes over to power the pump during driving. Hitting it like that over and over probably did it in (I'm guessing right now, but it makes sense.) The EFI relay should be checked at the same time. The EFI Relay costs like $12.00. Just replace that. The COR is around $125.00 t the dealer, but I got one at the wrecking yard for like $10.85 and it works great. There's instructions elsewhere in this forum to test the COR.
The Airflow Meter could be suspect as well.
Check all your vacuum lines.

Also:
My gas cap never hissed until I got my problem fixed. Now it hisses. Weird.

Yeah, I don't think its a fuel line leak. I spent some time under there yesterday with it running, looking for leaks. If its leaking, its at least not visible and I don't smell gas anywhere, like in the engine bay.

I just replaced the filter two days ago. The previous one had only 12k on it or something like that, but I figured I should at least try it since they are $15. I believe I at least have some pressure. I changed the filter as soon as I got back from the parts store (truck was hot). I got a real good spray of fuel, but can you have pressure, but too low of pressure? Looking through the FSM right now and I'm not finding a protocol to test it. Anyone know the page?

I checked the EFI relay a few weeks ago when this all started, and it tested good. But, I guess I can't be sure that its not sticking or something sometimes. It is the original. It probably wouldn't be a bad idea to just replace most of the stuff in that relay/fuse box.

Well, the more I've been reading tonight, it definitely seems like the gas cap and the starting issue could be related. Unfortunately, there seems to be plenty of different causes to start looking at. Sometimes I wish I'd never bought this 3.0. It's a rare day when my 22re truck can outsmart me, but this runner does it all the time.

You can bypass the COR and AFM switch by jumpering the +B and Fp terminals on the check connector by the engine bay fuse box. If the problem goes away, then you've narrowed it down quite a bit, and its easy to figure out which of those is the problem.

Heck fourwd1, I think you're a genius. Truck did the no hot start thing in the parking lot, but I carry a strip of wire in the truck as my diagnostic tool :) jumped those ports and it fired right up. I'm going to try to repeat this a few times today, but this might be the right track. Thank you!

No problem, let us know how it goes.