Start...Runs 6 minutes...Dies...Start....Repeat...

[Fatguppy]

1990 5sp starts fine. Runs very smoothly, when it's running. Then sputters to a stop after 6 minutes of running.
Bought this Ranger a couple years ago with mechanical problems. No oil pressure. Finally got around to fixing it - oil pump screen completely clogged with gunk. New bearings, timing belt, and we're back in operation.
Replaced the in tank fuel pump, filters, plugs, plug wires, and one coil.
Starts great, but after 6 min it just dies. If I try to start it right away, it won't. But if I wait 2 minutes - fires right up. If I keep the idle up around 2000 it doesn't die. Just runs and runs. Let up on the gas - dies with a little back puff through the intake.
Check engine light didn't come on until recently, so I pulled the codes.
KOEO: 11
KOER: 98 28
Memory: 28

I changed out the right coil pack. Nothing
I had the ignition module checked out at my NAPA, passed fine. Made sure it got good and warm on the tester.
So, I'm stuck! If it was a diesel I could tell you within minutes of the problem, but I just don't know the truck well enough yet. Anyone had issues like this before? Or know what I should try next?
A long time ago, I had a 924 with CDI ignition that did this same thing. Turned out that when the CDI unit got hot, it would shut off. Let it cool down, it would run again. Faulty CDI.
Any help would be great. Thanks!

 

[Sweersa]

Could it be a worn or faulty battery? Try running it off of another battery or a temp alternative power source.

 

[muscledrifter]

If it was the battery, the truck would run fine on the alternator alone. if it was the alternator, the truck would run till the battery dies, then wouldnt re-start. Fatguppy, i havent the slightest idea whats going on with your truck. but what i would try is to diagnose what causes it to die, wether it be fuel, or spark. and diagnose from there. good luck

 

[Sweersa]

If it was the battery, the truck would run fine on the alternator alone. if it was the alternator, the truck would run till the battery dies, then wouldnt re-start.

That makes sense. I just remember being told in the past if an alternator fails some heavily lead based batteries can actually partially recharge some after waiting a while on their own to an extent to get you running for a bit, then will die off again.

 

[kimcrwbr1]

put a timing light on it and see if it loses spark when it dies same with the fuel pressure guage

 

[scotts90ranger]

sounds like either the fuel tank isnt venting or the IAC isnt working right

 

[muscledrifter]

That makes sense. I just remember being told in the past if an alternator fails some heavily lead based batteries can actually partially recharge some after waiting a while on their own to an extent to get you running for a bit, then will die off again.

didnt know that they still made batteries with lead.... kinda scares me to think i may have a highley poisonous substance in an object that can explode if mis-treated.

 

[Fatguppy]

I'll check the engine with the timing light and fuel pressure. If I disconnect the IAC should the engine die? I've done that and it doesn't die immediately. I've even tried leaving the fuel tank cap off. Still dies. I'll check the vent line though. The battery is good. Even jumpered it to my running diesel.
Thanks for the advise!

 

[Sweersa]

didnt know that they still made batteries with lead.... kinda scares me to think i may have a highley poisonous substance in an object that can explode if mis-treated.

Hehe, I have no idea how old my battery is but it has a lead warning label on it and is Motorcraft. I am not the original owner but the truck is 13 years old.

 

[bcost882]

any codes?sounds like it might be fuel crappin out like leaning out to where it won't run...

 

[Fatguppy]

I listed the codes I pulled in my first post. Those were the only ones I could pry out of it! I'll attack it with renewed vigor in the morning!

 

[Fatguppy]

Couldn't wait till the morning! I tested the ignition. Tests good. Spark all through the shutdown. Took the intake tube off. Filled a little squirt can of gas, started it, shen it started to die I squirted a little fuel into the TB. Stayed running! It's leaning itself out to the point of fuel starvation.
Now, will a bad O2 sensor do this? Remember, it stays running at the higher RPMs. I tried the squirt can at the higher RPMs too and it ran even better, so the leanness affects the upper RPMs too.
O2 sensors are cheap so I'm replacing it tomorrow reguardless. Any thoughts.

 

[scotts90ranger]

ok, quick advise on the O2 sensor, it sounds like it could do it, but listen up

go and look at your sensor to see if it's a 3 or 4 wire sensor, '90 is the year they changed between the two, if you have a mass air flow sensor it's most likely a 4 wire, if you don't you probably have a 3 wire, if you have a 3 wire ask for the sensor for a '89.

also if you have a mass air flow sensor, take it off and clean it, it could cause the issue also, use mass air flow sensor cleaner not brake clean or carb clean or something.

 

[Fatguppy]

Update:
checked fuel pressure. Jumpered the relay so the pump ran continuously - 26-28 psi. Started it, ran it till it died and noticed that the pressure dropped to 0! Pump was still running though.
Bad pump or maybe it's sucking something up into the opening. But I think the pump is bad.
What pressure should I be getting at the rail?

 

[Jason]

Could still be an ignition module too. Ford didn't have any problem with that design. lol