dyeager535

Updated at bottom of this post, if you want to spoil the surprise.

1987/88 TPI setup.

Drove to the store today, ran fine. Parked it, went inside for an hour or two, came back out, would crank but not start. Not even an attempt like they typically do with bad timing or not enough or too much fuel.

So I pulled all the injection related fuses, all good. Checked for spark, got spark. Fuel pump ran, could hear it. Tried with throttle more open, no difference. Tried for a good five minutes, stopped since I didn't want to kill the battery, and I knew I'd need the right tools.

Let it sit about an hour, came back with my scanner and all my tools. First things first, hooked the scanner up. ECM checked out ok, and no codes. TPS ok, coolant and MAT sensor had believable readings. 45* ambient temp approx.

So no codes, cranked engine with scanner hooked up (per service manual) to see if RPM was reflected in scanner. It wasn't. But of course, the vehicle started. Idled fine, and I drove it home just now. No issues on the trip home.

Anyone got any ideas what I should be looking at in the future as a cause? Only things I can think of are temp sensor(s) or IAC. Don't know if the temp sensors can get "dead spots", but that is my only idea on that one. For IAC, I'm not sure what should be a "normal" count, but it was reading 60 as it idled. IIRC when the engine was off it was reading 150 or so, but I didn't really make a note of it, as I figured the engine off IAC count was unimportant.

It has done something similar one or two times before, but it just took more cranking than it should with the vehicle being already warmed up from driving. Nothing to the extent like today though. Similarly, the other "problems" were after the vehicle sat for an hour or so.

For one thing, I'm going to be sure to put that scanner in the vehicle "just in case", so I can look at the various readings to see if anything is wrong at that very minute. Just curious if anyone has any pointers on things to focus on.

Many of the things on the system are new, about the only things that aren't are the injectors, IAC, fuel pressure regulator (can't recall what it's real name is, the vacuum controlled one) and EGR.

Fuel pump, fuel filter, TPS, MAT, CTS, are all new. I fully understand new doesn't =good, but I don't throw parts at problems, especially with something intermittent like this.

Edit:
After having to wait over a year to work on the problem, update here so no one needs to read any further.

Went and got a new to me ECM. Replaced, problem gone. Got my new Ford injectors installed, sold my old stock ones, buyer had them tested, 3 of the 8 were "dead". Decided to install my "dead" ECM, and see what happened. Sure enough, problem no longer occurred. Go figure. Problem solved, bad injectors!

Cooper

I know you said you had spark, but I had a similair issue with my GTA about 5 years ago, and every time I'd actually have tools there it would start right up. Turned out to be the ignition module. It would never crap out when it was running, but it stopped it cold on startup every now and then, wait an hour or two and then start up. Just an idea.

dyeager535

It's a tossup I guess.

I mean I've not had enough experience to know whether or not an ignition module can allow spark, yet at the wrong time, or too weak to fire, etc. Since I was getting spark though, you'd *think* that wouldn't be the problem. IIRC, the EST bypass wire (I think thats what it is, the one you disconnect to set base timing) when unhooked is supposed to prove whether or not it's the ignition module...if it starts disconnected, it's not the module. I did try that test, and it still wouldn't start.

Really it does come down to spark and fuel, if both are present, it will start. If the engine temp is reflected right in the ECM, and it sparks, the only thing left that isn't easy to "prove", is fuel, and I'll make sure to bring my test light from now on in case this happens again.

I definitely agree its something to do with heat/cooldown, something along those lines, or else it would be more consistent...for the few times its acted like this (again not to the exact same extent, but similar) the time it sits after running seems to be fairly consistent.

Just hate the feeling that theres going to be that one time where I'm in a hurry or out in the middle of nowhere and it's going to act up on me again.

TheGreatJ

That wive's tale about the EST bypass is just that...a wive's tale. There is no truth to it at all, as the bypass wire only carries the timing info from the ECM to the module. It does not tell the module to trigger the coil, only how much timing to add.

A marginal module can very easily cause a problem with hot-starts. Any electronic component will be heat-sensitive, and these in particular are because they sink a lot of current in an enclosed space. That's why you HAVE to use the white grease on a new module...it's to help transfer the heat out into the dizzy base.

Next time it acts up, check the trigger pulse going to the coil with your testlight. That'll give you a definitive answer on whether it's the module or not. Just hook the clip end to the + battery terminal and probe the white wire at the coil. If it flashes while spinning the engine, the module is good, and you need to check your fuel pump.

Cooper

Also, I've seen the pickup coil in the distributor do similair things as well.

89Warbird

I had the same problem, it was an injector causing all the heartache. Replaced them all and not a problem since. Several different shops were stymied by this problem as well.

89Formula5.7

My "Hypercrap" chip caused similar problems to yours.