Hi, long time lurker, first time poster.

I acquired this truck a couple months ago and I'm pulling my hair out trying to figure this out. I bought it and drove it 4 hours home and it ran great. Now fast forward a couple weeks and it has developed a very strange issue. It runs great, however, it will randomly shut off instantly. its a manual so all I have to do is push the clutch in and if I cycle the key ignition, it will fire right back up and drive away. If I DONT turn the key off, and back on, it will just crank and crank and never start. So in summary, it stalls when driving, and requires a full OFF and ON cycle of the key to start back up. If I try to start it back up without turn the key to OFF first, it WILL NOT start, just keeps cranking. When it stalls while driving, I have to turn the key to full OFF and then crank it, she fires right up and runs... for another minute or two. seems totally random.

It will do this no matter what fuel tank I have activated. I can hear fuel pumps running when I cycle the key to KEY ON ENGINE OFF, and one pump will run, and if i change the fuel tank selection, the other pump will run so that tank selector seems to be OK.

This truck is the first year of the high pressure fuel pumps being in the tank so there is no frame rail fuel pump that is shared between both tanks.

I find it hard to believe that both fuel pumps would be failing exactly the same way.

I haven't hooked up a fuel pressure gauge to the truck to see if the fuel pressure dies right before the engine dies but I'm suspecting it has to be fuel related.

I'm thinking maybe there is a common ground both pumps share and may not have a good connection but I haven't been able to find anything.

Could it be a bad computer? That's about the only thing I haven't changed.

I did change the fuel filter very recently just as a routine maintenance since I didn't know when it had last been changed. It wasn't stalling then or giving me any issues.

Any insight is greatly appreciated.

Many Thanks!

I've attached a picture of the ole girl. 1990 F-150 4x4 4.9 I6 w/5 speed manual.

 

Perform the KOEO self test to check for active and stored fault codes. Post what, if any, codes you get and were they active or stored codes. Buy or rent a fuel
pressure tester. Turning the key off and then to start runs the fuel pumps for a couple seconds. It sounds like a fuel issue but don’t start throwing your wallet at the problem without doing any diagnostic testing.

 

If the computer doesn't have any bright ideas, I'd run it until it stalls/won't start again, then check for fuel pressure and spark to see which one has dropped out.

 

Hey guys, thank you for the suggestions. I finally had a day off work and I was able to do some troubleshooting.

I was able to pinpoint an ignition issue that randomly occurs and is fixed by simply doing a key cycle.

Ran fuel pressure and vacuum pressure tests.

Ran, idled, and revved the engine for a long time. I was able to get it to die several times. Fuel pressure was consistent at 50+ PSI. Even when it died or nearly died. The fuel pressure never dipped, very steady. So this test rules out fuel pumps or fuel starvation.

Vacuum gauge showed a consistent 13-15 mmHg. Vacuum reacted exactly as it should during rev tests. This rules out any vacuum issues.

Lastly, I hooked up an ignition light that runs in line with a spark plug and lights up with every spark of the spark plug. It was lighting exactly as it should and then the engine died. Trying to restart the engine WITHOUT cycling the key, it WOULD NOT START it would crank and crank and no fire and the spark light was not lighting up signaling that no spark is being sent. Once I cycled the key off and back on… Fired right up. I was able to recreate this several times.

So I’m summary, my issue is engine is running fine and suddenly dies because it loses spark and it will not regain a spark until you cycle the key. It will crank and crank but will only fire if I cycle the keys… very confusing.

Is it a bad ignition switch? Computer? Ignition coil or module?

Any insight is greatly appreciate!

 

I take it there aren’t any codes or at least none of the codes from the KOEO self test are ignition related?

 

Good work. The off-and-on-again logic sounds far too regular to be a flaky ignition switch, but it's still not a bad place to start. IIRC the switch is kind of a pain to get to on these. Might be easier to run it until it stalls again, then try to run codes. If the computer talks back, you know it's still getting power. While you're under the hood, check for power at the coil as well.

If all that checks out, pull the spout connector and see if that brings the spark back. If it doesn't, start checking ignition components. If it does, check the computer.

 

Hi, you are correct. Check engine light is NOT on. A check for saved codes gives me code 67 and 83.

 

I have heard about the flakey Ford ignition switches on the column. I was thinking that may be my issue, but from what I have seen, the truck won’t crank and all the lights on the dash are supposed to turn off, correct? My truck cranks and the dash lights are all illuminated as usual.

Before all of this, I put in a new coil, cap, and all new ignition wires. I was having misfire issues before this and I found the coil to distributor wire was completely corroded and I was surprised the truck ran at all. The original coil was really crusty looking too so I replaced that as well. Maybe my new coil is the problem? How do I check to make sure my coil is receiving the correct power? Do I check for 12V at the pigtail?

 

83: is the EGR open stalling out the engine?

67: my book says air conditioning compressor clutch switch fault. Is the compressor locked up?

 

I have installed a brand new EGR. I deleted the smog pump system, my truck had the 6 smog pump tubes going into the head that I had to plug up which required me to pull the intake. When I did that, I noticed how bad my EGR looked so I put a new one on while I was in there.

Even if the EGR had an issue, I don’t see how the EGR would be causing the engine to crank but no spark situation.

Air conditioning works great as well, no issues.

 

maybe-->Part 1 -Ignition Coil Test -No Spark No Start Tests (Ford 4.9L, 5.0L, 5.8L)

 

I have seen issues with those years with ignition switch problems. They seem to be aggravated by heavy key rings or other extra weight hanging from the key in the switch. Replace the switch and go from there.

 

Hi guys, thanks for all the tips and suggestions. That write up on how to troubleshoot a no spark situation is absolutely fantastic. Props to you for sending me that and props to the individual that created it. So much help! Truly.

I worked my way through the troubleshooting and process of elimination and I ended up driving to the part store and buying a new Ignition Control Module. The module that bolts directly to the side of the distributor. I don’t wanna jinx myself but so far, so good. I went for about a 30 minute drive and the truck ran flawlessly.

I will update my thread with any new occurrences. Hope this ends up being helpful to someone out there.

Many thanks 🙌🏻🙌🏻

 

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