Okay I hate to be the guy who never comes on the forum then come on here asking for help, but I am totally stumped at this point. I have a 86 f150 with a 5.0, I have done countless things to it. The engine is MAF swapped from a 94 f150.

It ran fine with this setup for a while, the only thing I have recently changed is I went from a one wire O2 sensor to the proper four wire O2 sensor. And it ran better for a few days. Then after test driving it to see how it handled with some new tires I mounted, I shut it off then went to see how easily it would start and it would crank but never fire.

It is getting spark, it is getting fuel. It starts fine when cold, just not when it is hot. If it does start when hot it starts like it had too much fuel. I can however, start it easily by removing the fuel pump relay while the engine is hot. It idles and runs fine, has plenty of cranking power.

I went through many connectors and dielectric greased them, checked the timing, replaced my ECT sensor the other day, tried a different ignition module on the distributor for the heck of it... Any ideas? I'm pulling my hair out over this one, I keep checking things with my multimeter and I'm not getting anywhere.

 

What computer are you using with that MAF conversion?
Any codes?

 

I had a distributor warp somehow and when it get hot, the distributor cap would expand and it'd give the same results. Get spark, get fuel... But I was getting a weak spark...

Food for thought lol

 

Something to think about...

And It was a BUG0, then I swapped to a Reman A9L the other day (after the starting problem came along) And it's still there. the A9L fixed a hesitation issue I had at cruising.

 

No one has any ideas? What components are active on, or determine the initial start up tune? Could something be shorting? Would the O2 sensor possibly cause this?

 

Plugs are all wet with fuel. Tried a new coil and ACT sensor, adjusting the idle/tps. Changed plug gap, changed timing. Still nothing, starts without fuel pump relay pretty quick. Cleaned battery terminals and underhood grounds. I think wiring may be a problem because I scanned for codes and got-
15, 51, 22, 53, 54, 81, 82, 96 All KOEO. I may buy a moates quarterhorse and try changing the startup settings, maybe the coolant is getting too hot and going past the hot start temp. This is the worst issue I've ever had with this truck

 

Just an important question for you.

When you have the "no-start condition" turn the ignition to the "run" position (not start) and listen to see if the fuel pump runs for a couple of seconds then stops, or does it/they run continiously ????

You need to try that and report back.

Conanski asked (above) an important question too.


Bob

 

Yes I hear it prime for a few seconds then shut off. I have also ground the fuel pump on the self test connector to see if it would start that way. No different. Put my foot at a all different positions on throttle, no difference. The way it sounds when cranking is exactly the same as if you pulled the coil wire off and cranked it. But I am getting spark. And if spark was the issue then it wouldn't fire right up with the fuel pump relay removed. I am wondering if the PIP could be heat soaked and messing with the injector timing/duty cycle?

 

I figured my issue out. I ended up having the signal return (SIG RTRN) wire one pin off in the EEC connector. It goes to every sensor on the truck. Hooked it up, everything was fine.