My dad's got an 1993 E-150 5.0. It's started cutting out on him a little (really just running rough from time-to-time). The real problem is that it won't start when it's sat for a few hours.

He called me up to his house a couple of days ago and I hit it with a shot of starter fluid in the breather. It started right up. I was a little surprised; made me think fuel problem. I had the fuel filter replaced, starting with the least expensive and easiest thing to replace. Same problem. Pop took it to a mechanic (ex-dealer's shop) who charged him $189 to "diagnose" a bad computer. Sounds a little strange to me, but...

I actually spent 10 minutes with Pop and the Van tonight. It has a loud fuel pump, no problem there. He turned the key and nothing but crank. I had Pop leave his key in the ignition with the pump running for a few minutes while we chatted. Sure enough, a couple more tries and it started right up. I'm not a mechanic, but this is sounding to me like a pressurized system that's just not holding pressure. Could it be as simple as a leaky fuel line? Does that make sense? Or, is there something I'm missing in the PCM/ECM that would actually cause this?

I'm a little concerned that this ex-dealer saw an 80 year of man driving a beat up old van and figured him for an easy mark - never mind my mom's wheel chair lift inside.

 

I would say a bad computer but he could have gotten that information for free here.
Anytime the fuel pumps come on and run for more than one second with the key on and the engine not running or cranking it is a bad computer most of the time. When this happens the fuel injectors will not be firing while the engine is cranking and that is why it is not starting. You can check that with a NOID light plugged into one of the injectors plugs.

The few times this is not the computer you will have bad grounds to pin #40 & #60 of the computer or no power on pins# 1, 37 & 57 with the key on. But as I say most of the time the computer is bad.

What is wrong with the computer is that it has a bad Capacitor inside that causes all of this. Some just replace all of the Electrolytic Capacitor in it and they are good to go or you can send it off and they will replace them and send it back to you.

 

Wow! So the computer runs the pump to build the pressure then cuts it off to fire the plugs. I can buy that. But why does it start right up with a shot of ether? That seems to work every time. - Or, after it sits for a few minutes with the pump running?

I did go online and look for used computers and found them as cheap as $25. Not sure what kind of shape they'd be in for that kind of money. I did manage to repair one out of an 83 mustang a few years back, so it might be worth a shot.

 

Oh... the mechanic did include the "repair" of a bad ground in the $189. Sounds like I might need to quit doubting him!

 

Well not quit like that.
What happens is the computer has a one second timer in it and when the key is turned on or when it see a PIP it will run the fuel pump (it does it by grounding the fuel pump relay coil).
The PIP from the distributor will come faster than one second while cranking or when the engine is running. So the fuel pump will run while the engine is cranking or running.
Yes the first one second of run time is to prime the fuel system.

 

Also the computer does not fire the plugs, the ICM (Ignition Control Module) does that.
The computer will tell the ICM once the engine is running how much to change the Ignition Advancement (spark).

 

Okay, I think I'm catching on... wait, no I'm not. I get it that the computer's not turning off the pump, but why does starter fluid start it right away? Does it have to do with the spark advance?

 

No it has to do with the computer not firing the injectors. But you have spark so starter fluid will start it. It may stay running if the computer now wants to fire the injectors or it might die if the injectors are not firing and it runs out of starter fluid.

 

Okay – we’re getting a computer. In the mean time, you seem to understand this stuff pretty well and I want to learn. So…

The mysterious part is that the starter fluid starts it right up and it keeps going. There’s no hesitation or other starter fluid like symptoms. Maybe the computer’s getting signals that tell it the engine’s running and those signals override whatever’s keeping the injectors off? That seems reasonable.

Then the next question is “Why does it start if we let the pump run for a while before cranking?” It makes sense that a weak pump or depressurized line could cause the computer to wait until there was adequate pressure before firing the injectors. If the starter fluid caused the computer to fire the injectors without adequate pressure in the line (assuming that’s possible), it seems logical that the engine would sputter and die when the fluid was used up. (I guess that debunks my theory of a depressurized line.)
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If the purpose of the capacitor you mentioned is to the delay the injectors while the line primes and it opened, the rest of the circuit would never reach the voltage it needs to cut off the pump and fire the injectors. I guess there could be another “override” circuit that eventually fires the injectors after some amount of time passes? However, when we start it by waiting, it “hits” a few times before actually starting – almost like it was flooded. Thoughts?

 

What I described above was for a stock system that no body has changed any wiring from stock.

It is possible that the fuel lines have drained dry and the pump has to pump for a while before the engine will run on the fuel from the tank. But it should start without the starting fluid after it fills the lines.

But as said above the fuel pump should only run for one second when the key is turned on and any longer than that with the engine not running or cranking is a bad computer most of the time.

You say the pumps run all the time the key is on and the engine will not start but will start right up with starting fluid and keep running. I have not heard of one doing this before if you have stock wiring.

It is possible that a ECT sensor can keep it from starting if it tells the computer the engine is hot when it is not. But that does not explain the fuel pump running all the time the key is on without the engine running.

The computer has no idea how much fuel pressure there is. There is no pressure sensor for the fuel system.

 

sounds like we may have a couple of things going on... Pop told me last night that he heard a squeeling noise coming from the rear of the van. I can't image what it might be other than breaks. Have you ever heard of a fuel pump squeeling?

oh - no one's touched the wiring that I know of

 

Never heard of a fuel pump squealing.
But squealing to one is roaring to another.

Have you check to see if there are any codes in CM?
You may also want to check the fuel pressure with a gauge.

 

Squeeling pump didn't make sense to me either. He's heard the normal pump noise and is convinced it wasn't that. The problem with the brake theory is that he said the noise was there sitting still. I'm wondering if there's something else in the back of the van that might be causing the noise.

There are codes but the usual suspect parts houses couldn't pull 'em. Main excuse was that the van was too old. Figured I'd have to find the magic sequence of key, pedals, and tongue position then count flashes or something.

I thought about a fuel pressure guage or measuring the output. I really haven't had a chance to do much at all with it yet - just research and spray starter fluid at it. I haven't even had the breather off. I'm assuming it's fuel injected. My brother-in-law isn't so sure. [1993 - another research topic]

 

Yes a 1993 would be fuel injected.
It is also SFI and Mass Air.
It is also OBD-1.
For codes check out this link:
http://fordfuelinjection.com/?p=13

 

ah... that's bringing back memories. That's how I had to ge the codes out of an '83 mustang almost 10 years ago!

Do you happen to know where the computer is in a 1993 van? We've been told that we need the numbers off of it to check the replacement.