92 F150 cranks but won't start
 

Hey,

So I have a 92 F150. 228k miles. On January 27th on our way home, the harmonic balancer busted. We got that fixed and everything was good for 2 days, and then my truck very quickly went downhill. It started by not getting any power when driving at any point. It bogged down and I would have to have pedal to the floor to go 25 mph. It finally just quit moving even with pedal to the floor. We parked it, and then it wouldn't start. Sometimes it would, but it would die immediately. We thought, oh yeah it's the fuel pump. So we changed that. Truck still won't start. We got it started with starter fluid, so we decided to change the throttle position sensor. No change. My husband was able to start it with the pedal to the floor and keep it running, but as soon as he took his foot off the gas it died. We checked the timing and it's fine. It has spark. The battery is fully charged. It has fresh fuel. He checked the fuses and they're all good.

Any ideas would be extremely helpful because we are moving in about a month and we really need to get it fixed.

Thank ya'll!

with the engine fully warmed up, pull codes .
also, test fuel pressure with a gauge.

fuel pressure regulator possibly. as its getting fuel but seemingly not enough. you might think about running some seafoam through it to clean out the fuel system. also might wanna change out the fuel filter.

just some thoughts, hope it helps.

Fuel pressure is 45 after changing the fuel pump out. We changed the fuel pressure regulator and the fuel filter first thing. We regularly use seafoam. Only codes we could get was the 111 and 512

Continuous Memory DTC 512 indicates the PCM has experienced a power interrupt in its Keep Alive Memory (KAM) circuit.

NOTE:
If KAPWR is interrupted to the PCM, for example when battery is disconnected, DTC 512 may be stored in Continuous Memory.

If you have not disconnected the battery then you may have a bad PCM Computer or bad wiring to pin #1 of the PCM.

Is there a way to test the wiring to the pin? Or test the PCM? Or do you just have to change it and find out? We've never messed with the computer before, so this is all new.

Pin #1 in the PCM plug should have power (battery voltage) to it at all times.
You could unplug the plug and test for power at pin #1 while shaking the wiring harness.
Or while it is unplugged remove the pos battery post and check for continuity between the pos battery cable and pin #1 of the PCM plug.

Diagram below shows pin #1 position.
http://i54.photobucket.com/albums/g9...pshjwpmrzo.jpg

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Alright great, thanks! We'll check it out later after work

Okay. Pin #1 has voltage to it. We opened up the PCM, and noticed quite a bit of corrosion on it. Would this cause my problems?https://cimg7.ibsrv.net/gimg/www.for...34df234413.jpghttps://cimg8.ibsrv.net/gimg/www.for...6c40a0e053.jpghttps://cimg9.ibsrv.net/gimg/www.for...7b4eb7790c.jpghttps://cimg1.ibsrv.net/gimg/www.for...2918e0486c.jpg

yeah. Those capacitors are bad, have leaked all their magic onto the board.
Google "replace capacitors", watch a couple of youtube videos. It's easy, but not a guarantee the board's not ****ed.

Yeah, those capacitors are shot.

The bad thing is that you have don't know how badly corroded it may be beyond the surface coating. My last PCM failed and the Capacitors leaked all the electrolyte fluid out, which in turned destroyed the traces on the surface.

You would have to remove the damaged capacitors, throughly scrape the protective coating over and see how badly damaged the underlayer is.

1. You can try to replace them yourself
2. Find a TV, Electronics repair shop that can replace the capacitors and Repair the surface trace IF needed.
3. Go to the auto part store and see if they have one readily available.

I list #3 as a last resort. You will have a warranty with it, but you don't know​ any history from it or how it was repaired.

Hopefully the corrosive fluid didn't​ eat through.

It also looks like that PCM was repaired before as one of the caps is stick up far from the board and that is not how they are made.

We'll get it fixed then. What do ya'll reckon the odds are that it's just this causing all my issues and not that plus something else like the fuel injectors? I've been without my truck since january due to the harmonic balancer busting and then now this. We are moving in May and we really need it to be running D:

The odds are a replacement PCM will fix your problem.
Not saying you might have other items but you need to get the PCM problem solved first.

I sure hope there is nothing else haha this has been a real fiasco. We'll get the PCM taken care of. I'll let ya'll know what happens after that! Thanks so much!

The jy is a solid source for inexpensive computers. Depending on your transmission, you may find a few of them for less than 50 bucks.

Well, got the PCM fixed up and put in. The battery was drained completely so we had to leave it on the charger all day. Came home and tried to start her up...fired right up, but started to idle rough so I gave it gas. After a little bit of the rough running, she smoothed out. Left her running for five or so minutes, sounded great. I decided to shut it off and try starting it up again, but now we're back to the cranks but won't start except when I put the pedal to the floor. Even then, it starts but dies right away. Any ideas now?

What's your fuel pressure immediately after shutdown?

PSI is 38 immediately after shutdown.

Does it hold 38 for an extended period of time?

Yeah it holds 38. We checked the timing and it was perfect. We are at a point now that it starts, and will run without dying. But it is extremely rough.

Can you refresh in a single post what you've done so far?

After replacing the harmonic balancer and crankshaft bolt that busted off, the truck ran rough and eventually would not move. We then tested the fuel filter to make sure it was not clogged. After that, we changed the pressure regulator. Then, we changed the fuel pump. Before we changed the fuel pump, the PSI was around 24. After we changed it, it stays around 40 PSI so that did help. After that, we checked fuses and relays. We were able to get it started with starter fluid, but it would die immediately. Then we replaced the throttle position sensor. We checked for spark and that was fine. We tried pulling codes, got a 512(Keep alive memory test failed) and that is all. We then replaced the PCM because it had power to the pin and it had a lot of corrosion on the capacitors. Once we changed the PCM, it does stay running but it is extremely rough. Not enough to actually drive or anything.Then we checked the timing and it was perfect.

About the only thing left is the MAP sensor, ECT and ACT sensors.
Check the vacuum line to the MAP sensor also.
The MAP, ECT and the ACT sensor can be bad but you will not get any codes for them if the Computer does not understand that they are bad. But you can test them.

You might also try blocking off the EGR valve until you get it going.

Does it run better on starting fluid, or the same?

I.e. does it run smooth at any point when running off starting fluid.

Where are those sensors located? And how can we test them? We were thinking about testing compression next.

Also, it runs the same with starting fluid. Real rough.

Note the MAP sensor can also be tested with a hand vacuum pump and a Dwell meter or a Frequency meter.
See attached PDFs for testing.
The location depends on what engine you have as you have not stated the type.

We'll try testing those tomorrow. It's a 5.8l 351

The three locations in red:
http://i54.photobucket.com/albums/g9...psjyj05htw.jpg

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Just on a side note while we're trying to figure this out, how much do ya'll reckon we could get out of this truck if we have to sell? We are moving first week of May, and can't leave it here so we will have to sell if we don't get it fixed within the next couple weeks. It's a 1992 F150 5.8l 351 4x4 with 228k miles. 4" bds suspension lift with 33s BFG all terrains. Dual exhaust with glass packs put in a couple years ago. Reman transmission put in last year, replaced transfer case as well. The door latch is broken on the driver's side, and probably needs the dash replaced. No rust. But in a non driveable condition, how much you reckon we could squeeze out of it? I love this truck to death but life happens. I have no idea what to even ask for it since it won't run well.

We did a compression test tonight. Are these too low? Haynes Manuel says lowest cylinder must be at least 75% of highest cylinder. Which it is.
Results:
Cylinder #1 = 80psi
#2=90 psi
3=90
4=85
5=85
6=80
7=80
8=90

Okay, so once we put all the plugs and wires back on, we started it up and it ran okay. Let it sit for a little bit, then tried putting it in drive and it died. So we decided to just try a different MAP sensor, now it won't start up again. We put the original MAP sensor back on, still no start.

Would it be a good idea to test the fuel injectors next?

You say you still have fuel pressure when it dies and it sounds like it will start and run OK when cold but not if it had ran and got warm.
This could only be the Ignition Coil, ICM, PCM or the PIP sensor.
I know without rereading your thread that you have replaced some of these parts.

You need to put a NOID light on it when it does not start, you can rent them from most auto part stores and get your money back when you bring them back.
You also need to check for spark when it does not start with a spark tester, they are very low cost.

We've replaced the PCM, but none of the others. Checked coil for spark, but engine was cold at the time. Is there a way to test those other than just replacing? I guess we need to get out there tomorrow and start it up so it can warm up and we can check for spark when it doesn't start again. But it definitely is looking related to the engine warming up.

Gee Whiz buddy, have you read post #17 above in your thread?

No sir, I'm sorry, I didn't see that. Thanks, we'll try it

sgoodman95: You may want to take a look at my experience following Abraham's methodical troubleshooting approach here for an example:

https://www.ford-trucks.com/forums/1...l#post17086763

From my reading electrical problems are hard to diagnose properly but very quick to fix, while mechanical problems are easy to diagnose and are slow to repair. It requires a different mindset. But if you commit yourself to follow the troubleshooting steps without cutting corners, you will find the problem. Take a look at all of Abraham's troubleshooting approaches for your particular engine here:

Ford Main Index Of Tutorials

I have a 95 F150 with the same engine and mileage. I have been reading this and went through the same no start issue about 2 months ago. Changed coil, checked ignition module, pcm, etc. All the things you have done. When I checked the engine coolant temperature sensor, it came apart when I tried to unplug the wires. Replaced it and the problem went away.