Hi Everyone,

I have 2 problems starting my 93 F-150 that are driving me crazy and don't want to just start swapping parts on a fishing mission. These fuel-injected engines that were built before OBDII, in my humble opinion, are the hardest to diagnose!

Both of these problems started at about the same time a month ago.

NO check engine light has come on.

1. On the first start of the day, when the engine is stone cold:2. On EVERY OTHER START that day, regardless of how long the engine has been off (5 min or 5 hours):Any suggestions to solve these greatly appreciated!

 

1st thing to remember on EFI engines is that when you floor the accelerator before attempting to crank, you essentially tell the PCM to shut the injectors off to prevent flooding the engine.

What engine are we troubleshooting?

Have you checked fuel PSI?

Even though the CEL isn't on doesn't mean there couldn't be stored codes relating to the problem. Try checking before attempting any part swapping, as that gets pricey.

 

Thanks for the quick response - I went out a few min ago and messed around with it some - more info below.

So I've been driving the truck this morning so it is hot. I experimented some more with the second problem.

The hot engine will start, run for a fraction of a second and die.
If I goose the gas at just the right time while it is running, I can occasionally get it to recover and run.
If it dies, the ONLY way to get it to start is to hold the throttle most if not all the way open and crank it for 2-3 seconds - it will eventually begin to start to fire and then I let off the gas and it starts.

5.0l / 302

Just did - 33 PSI at idle, will jump to 37 and dip to 30 as the engine is revved but always comes back to 33. Does this on either tank (2 tanks with 2 pumps)

I pulled the codes

KOEO - 334
Continuous - 334
Running - 116, 334, 225

334 is an EGR
116 is temp high/low - as far as I could tell the engine was at operating temp during the testing
225 is knock not sensed

225 got me to thinking - so I went and took a hammer and tapped on the back of the head and an exhaust stud to see if the RPM dropped and they never would (not sure if this trick works on this engine or not)

I doubt the EGR valve would cause this kind of problem but could the temp or knock sensor failures do it?

RP

 

I don't have me code definitions with me, but if 116 refers to ACT or more importantly the ECT sensor, then yes, that's gonna be a game changer in how it runs.

 

New member here and I have a similar problem which is why I joined.

I have a 93 150 302 tha will start fine, run great for a while and then just quit! It wont start back up for a bout an hour or so. I can start it and let it set, shut down and restart multiple times. Not until I drive for a short time will it shut down and not restart. It has a spark and fuel ( as checked at the port on the rail) but Like you I dont want to swap parts and just guess. Any help out there?

 

It is the ECT and along with the knock sensor, after much internet research, have learned that either or both of these can cause wacky engine running. Will fix both and then see what happens.

Thanks for reminding me about the codes - after you mentioned it, I recalled that they may be stored even without a check engine light. Amazing the stuff we know but don't remember

 

Sounds like the OP has a bad fuel pressure regulator. Pull the hose off the nipple on top and turn on the key. If fuel comes out it is bad.

If not that you may have a fuel transfer problem with both HP check valves bad.

The second guy could have a problem with the PIP sensor, Ignition coil or the PCM Computer.
Sometimes a fuel pump will quit also when warm.

 

You also have a 5.0 that if it hasn't been rebuilt has 260,000 on it. Your first problem with the miss that goes away as it warms up sounds a lot like a lifter leaking down overnight since it changes with engine rpms but goes away after it pumps up and is fine the rest of the day.

 

I thought about the FPR being bad. Its easy to diagnose if you pull the vacuum hose and fuel runs out.

 

Pulled the FPR vacuum hose and no gas came out and there was a vacuum on the line from the intake so I assume this is OK. I think I need to fix the codes first and then see what problems remain.

 

I forgot to mention that the engine and tranny were rebuilt 18,000 miles ago and the lifters were replaced. The old ones were pretty badly varnished and I did not think cleaning them could get all the gunk out of the innards. I HOPE this is not a problem. I don't look forward to getting to a lifter again...

 

You need to get the fuel issue fixed first. When you say the fuel pressure "dip to 30 as the engine is revved" you are saying you have a fuel starvation problem. In other words your fuel system is not able to supply the needed supply of fuel to the engine.

 

There are a bunch of electrical parts - sensors and actuators, everything from the TPS to the injectors to the ECU that can and do begin to wear at the mileage you have. I just replaced a whole bunch of stuff, and each part I put on made noticable improvements, most notably plugs, injectors and the distributor, as well as the O2 sensor. If your O2 sensor is older than say 10 years, and it is taking a while for things to even out, the O2 sensor could not be heating... though you are not getting a 41, it's one of those things that without having a scope could be cheaper to replace than to have tested. (assuming you can get the old one out) You could run a cylinder balance test (I've tried this and must be doing it wrong) but if you have a specific cylinder that is not right you can diagnose that. You could also look at your plugs for evidence of misfiring...

 

OK so I did the ECT test procedure and it is bad. It is reading 135,000 ohms resistance even when the engine is near op temp.

That resistance reading would be for a very cold engine.

This would explain how it would start better when cold - the computer is actually getting a correct signal for that temp whereas when the engine is warm, it is not - and hence would have incorrect inputs and start problems.

Now on to the knock sensor...

 

I think I would look at the fuel problem first.