Engine won't start

[toolmanx]

I’m stuck. I have a 7.3L IDI on an early 94 F450 that won’t start.
This is a project truck.

Below are the tests I done so far:

At the schrader fitting of a "new" fuel filter I have 6 psig. I have
cycled the cold start solenoid and the fuel cut off solenoid and
they both sound fine. The starter turns perfectly. The truck
started and ran fine until I parked it for 2 months. When it failed
to start, I put in a new fuel filter assuming that was just old and
not passing fuel efficiently. That didn’t help.
I pulled one drivers side glow plug wire at the front of the engine.
There is voltage to the glow plug and that particular plug has
low (good) resistance.

I unscrewed the nut on the same cylinder as the glow plug a few turns.
The tubing is so tight when I tried to move it to break the seal, that
I didn’t expect to see fuel when I cranked and I didn’t.

I’m not sure what to do next. I could unscrew the first 3 injector
nuts on the drivers side and crank it but unless I can break the seal
on the tubing I doubt if I will see anything. I may be wrong. Should I
completely remove the nuts on the tubing and slide them up the tube
so I can see the tubing as it enters the injector? That will be my
next step unless someone says “No, don’t do that”. I’m trying not to
take apart anything I don’t have to because everything is so tight.
Using as much torque as I did just to unscrew the one tubing nut
exposes me to breaking something on the injectors. I’d hate to add
more expense to the job. I already have too much in this old truck.

Is there a check valve in the high pressure pump feeding the return
line that I can get to easily and see if it is leaking through? I
need an exploded view of the HP pump. Is there one available on the
web?

I’ve always avoided taking off and dissembling an HP pump for fear
I would have trouble resetting the timing. I’ve had a number of
diesels in my day but stayed away from the HP pumps. I could use a
step by step on setting the timing of the pump if I have to take it
off and tear it down. Any idea where I can get one on the web?

Toolmanx@ij.net

[Snotzalot]

Don't go messing with the return lines and caps!

Charge the batteries fully, plug in your block heater for 3 hours and try again.

How long does the WTS light stay on when first turned on?

Any white smoke out of the exhaust when cranking?

[toolmanx]

Me and my truck are in Florida. Yesterday when I cranked with the one nut loose the outside temp was 72 degrees. I don't think a block heater will help.

I had just charged the batteries before cranking. That's why it cranked so well.

I didn't see any smoke at the exhaust but the exhaust system is pretty long and I don't crank too long at a time. Don't want to ruin the starter. Smoke would have a big area to build in before comming out the back. To be honest though, I didn't look.

I don't have a WTS. The truck came with a relay that clicks a few times and you watch the voltmeter pulse. When it stops pulsing, you can crank the engine. This worked fine before I let the truck set for so long.

[Snotzalot]

Did you fill the fuel filter with diesel before installation? Did you bleed it after installation?

[Plywood]

When it sits, and when you change the filter you get air in the fuel lines.

All you need to do is bleed the fuel system through the filter by opening the wing nut at the top of the filter head or by depressing the schrader valve while cranking. Bleed it til you have fuel coming out with no air. Close whichever valve you use while still cranking so air dosen't get back in. Use an assistant or a remote starter button to crank it. Don't crank too long and burn up the starter though.

Then bleed the injectors by backing of 3 or 4 of those nuts at the top of the injectors about 3/4 turn while cranking the engine at full throttle. Best to do this with the engine cold (unplugged) or with a jumper wire to the cold start advance. They will simply get wet and that's when they are bled.

[toolmanx]

The engine would not start before I changed the fuel filter. That was why I changed the filter. After installing the filter, I unscrewed the schrader valve assembly and put fuel into the filter until the fuel ran out. I then rigged a fitting and gauge and screwed that into the female pipe thread hole. The pressure while cranking pumped up to 6 PSIG.

After replacing the schrader valve I tried to start it. No dice. I then unscrewed the nut on the front drivers side injector several turns and cranked again several times. No start and no fuel around the nut.

Tomorrow, if it doesn't rain, I will hold the center of the schrader in with a narrow punch and crank until fuel comes out. If it doesn't start, I will try that approach of loosening 3 instead of 1 injector nuts.

[Plywood]

Ok, what I meant was that when it sits a long time sometimes it won't start due to if you have any sort of air leak at all the fuel will drain back to the tank over time and it will need to be bled to start so therefore creating the starting problem then.

So when you changed the filter it let even more air in (if my guess is right).

The fact you had pressure dosen't necessarily mean that it was fully bled, although that is good to know that part is good.

When you bleed, you have to do it in order of filter first, and then injectors. I actually bleed all injectors at once, but some members report good results just doing three.

Good luck!

[toolmanx]

Today has come and gone. I got good flow from the filter with no air just fuel. Fuel came out or more exactly, wetted the loose nuts. Still won't start although I felt it might be trying a little.

[osufireman]

Originally Posted by toolmanx

I don't have a WTS. The truck came with a relay that clicks a few times and you watch the voltmeter pulse. When it stops pulsing, you can crank the engine. This worked fine before I let the truck set for so long.

Do you mean you don't have the light physically in the dash or it just doesn't come on?

My WTS light never came on when I bought my truck and I had to crank many times to start even in ambient temp (70's) during spring.

Since you have good fuel flow out of the schrader valve, with no air, have you diagnosed the GP system? I believe the clicking is the GP relay/controller cycling the GP's, but that should happen when they have glowed for 10-15 sec and are all warm, not immediately after turning the key IIRC.

That's where I would start (and had to with my truck).

[toolmanx]

I believe you are correct on all fronts. My truck came to me as I described. No light. However, as I was instructed by the seller, I turn on the ignition, wait while the plugs heat up and when the relay finishes cycling on and off, then I crank. This worked perfectly until I let the truck sit for two months or more while I worked on several other problems the truck had. I used a volt meter on one of the plug leads and the plugs are powered up, then as the relay cycles, the voltage cycles on and off. Then I crank.

[Snotzalot]

Proper heating of the gp's the relay doesn't cycle. After correct glow the gp relay will cycle.

How fast does the relay start to cycle? 10 or more seconds, or right away?

[toolmanx]

You guys might be on to something. I have not checked the time before the relay starts to cycle. I downloaded an article where someone put a push button in the relay circuit to be able to hold the GP on manually. Care must be used then to not over heat the GP's but I might try that. It will take a little time since my relay is way up under the dash.( I know, why there?) Anyway, I will either try to hold the glow longer or perish the thought, spray a little ether in the air filter. I hope I don't blow a piston. I've got to get the engine going. I am paying to keep my truck where it's sitting and commuting 35 miles each time I go there to work on it. I need to get it home soon.

[Plywood]

It's likely the problem could have something to do with the other repairs you made during the 2 months it sat that you didn't mention before.

[7bicks]

Fuel coming out of filter and not coming out of the injector lines most likely is a bad IP. Open a line or two at the injectors and check for a good flow of fuel, not just a few drops. Loosen the nut and pull straight up on the line bending it very slightly so you can see the end. Have it cranked over and watch.
It no fuel after time then either the FSS is bad/not working or IP quit.

You can also remove the top cover of the IP and look for fuel in there, if it is full then IP is shot.

[toolmanx]

The work I did was all on the brakes, parking brake, and general lube under the truck. When I got this truck it had zero brakes. I drove it to where it is now using grandma gear.

I checked every glow plug today to make sure they had low resistance. All look good. The time it takes to get the relay to cycle is about 10 seconds. The same as before I parked it. I'm about ready to try ether.