Glow plug/wait to start light inoperative?

[Muley7715]

I have a 2000 F-550 with 7.3. It has always been extremely cold natured, requiring a night of plugging in the block heater if it's the least bit cool. Upon starting when cold, it "racks" for a few seconds then idles rough but runs great when thoroughly warmed up (meaning after idling for around 10 min. on cold mornings).

This evening when I got ready to leave work, the "wait to start" light didn't come on when I turned the ignition switch. Naturally, it wouldn't start at all, so I called my wife to come get me and fetch a can of starter fluid from another truck. The batteries are almost new and showed a good charge. The strange thing is that the OD off light, on the shifter, was on when I turned the ignition on and could not be turned off. I tried several times to start it with no light coming on and finally just waited for the ether. Just as I told my wife to spray while I cranked, the light came on normally, I let it go out, and it started without issue. She never had to use the spray. When it started, the OD light went out.

Is there a safety switch on the tranny that could have caused all of this ? I had this happen one other time but eventually the glow plug light came on, and I was able to start the engine. I did have one bad battery then and replaced both thinking that was the problem, but tonight we're back to square one.

Does anyone have an idea what this could be ?

[JSchuricht]

Your gonna need to get the truck scanned for codes, and don't do it at Autozone. That's not the normal behavior of the lights. The WTS light isn't linked to the glow plugs and it sounds like you have a glow plug issue. Check the GPR it's the most common culprit.

[jesilvas]

Please don't use ether . . .
Unless you manually make sure the glow plugs are not engaged (ie, disconnect the wires from the relay)
But yea, might wanna get it scanned to be sure. Look in the 7.3 sections for the GP and GPR issues and fixes. Easy stuff.

[Muley7715]

About a year ago, I had the Glow Plug module replaced just to see if that would help the cold starting problem, but it didn't make any difference. There are two very similar looking modules on the top of the engine. Is the one for the glow plugs forward or aft ?

As for the ether, it is always a last ditch effort, and I hate to use it. In this case, my truck was sitting under a "security" light out in the boonies in a neighborhood known for things getting stolen. The truck was full of tools, chainsaws, basically everything I work with, and I'm afraid only the indentations in the grass from the tires would have been left when I got there this morning.

BTW, I would rather it be in total darkness than under that light. All that does is help the crooks see things for easier theft

[JSchuricht]

One is for the Air Intake Heater the other is for the glow plugs. You may have a bad harness or burned out glow plugs.

[Muley7715]

OK, it happened again this afternoon, and the truck is stranded in one of my pecan orchards with virtually every tool I own in the boxes and in the back

Here is the complete history of this problem so maybe a light will go off in someone's head.

About three months ago, I tried to start the truck and the "wait to start" light wouldn't come on with the ignition key. Maybe 30 minutes later, it started just fine. I replaced both batteries, since one was bad, and I thought the weak battery might not be supplying enough juice to the glow plugs and starter. For three months, no problems.


All was well until last week when this happened again, only this time the OD indicator off light on the shift lever stayed on and could not be turned off until the "wait to start" light came back on and the truck came to life. That was maybe an hour after the initial problem, and the OD light then went back out.

Today, no glow plug light and no start, but the OD light did not come on at first. I went back to lock everything up 2 1/2 hours later, and the wait to start light operated normally, and the truck fired right up. However, it cut off after only 5 minutes as I was driving out of the orchard. It has never just stopped running before. The OD indicator light came back on again. Now the truck is dead in the water.

The F-550 bucket truck, loaded with all kinds of tools, tips the scales at over 14,000 lbs. It's gonna be tough and/or expensive to get it to a shop with diagnostic equipment. If I can test/replace anything myself, then I'm game to try.

Any more ideas ?

[jesilvas]

CPS?
The GPs aren't causing a hard/no start. It's some sensor or wiring or something else. Loose UVCH?

[Muley7715]

jesilvas CPS?
The GPs aren't causing a hard/no start. It's some sensor or wiring or something else. Loose UVCH?

CPS and UVCH

What are those and where are they located ? Did I mention I'm not very mechanically inclined, but I can swing a hammer pretty good

[jesilvas]

You can search on here for them but the CPS is the camshaft position sensor. Next to the crank pulley, just passenger side and down from it.
UVCH is the under valve cover harness. Two of them, each one has 8 wires. 4 for the GPs, 4 for injectors. The connections at the center of the valve covers may come loose or burn up.

[Muley7715]

I was all set to take the truck to the local Ford dealer, about 25 miles away, but I was worried it would quit in the middle of nowhere, which is between home and the dealer. I had another truck in the tire shop near my house, and the owner, who loves the 7.3 engine and drives a heavily modded dually, said he'd go look at my truck.

He made a few calls to friends and decided that it was worth a try to replace the computer, just to see if that was the problem. He had three units, all with different codes, out of wrecked vehicles, etc. He collects various parts, "just in case". I went to Macon, about 25 miles away, to pick them up. After struggling to get the old computer out (y'all know where they put the thing) he checked the code and found one of his three a close match. We stuck it in and all was well again The codes were not exact, but, so far, everything seems pretty normal.

I drove to his shop to pay him and told him that the unit must have been from a fancy truck as I now had leather seats with power, a console, and 4x4 I think one of the guys hanging out at the shop believed me.

The cost for computer and labor, $250.00. I shudder to think what it would have been at the Ford place

I think we got lucky, and his diagnosis was apparently right.

But he did tell me I needed some injectors