So I recently purchased my second 7.3L vehicle. This one is a 1999 E-450 Ambulance. 167k miles on it. Purchased it and had about a 300 mile trip home. Engine starts and runs smooth hot or cold. Trans shifts good.

Monitored trans temp, oil temp and a few other items via Torque.

Twice during the trip I had very odd behavior. Once climbing a reasonably steep hill on the interstate at about 65 mph while running cruise control, the truck did two big bucking/surges. Like over a second was probably half the power or accel cut and back on power. The check engine light came on imediately and I cut off cruise control and dropped speed. I stopped at a rest stop that happened to be within a mile.

Engine idled fine at the truck stop. Temps were fine. No fluids puked out, etc. I shut off the engine, and did a key on and there were no codes read by Torque and the check engine light did not come back on. Humm..

Second event was during another hill climb and the engine just stopped running (like I turned the key off). Truck coasted down from about 60 to about 40 then the engine re-fired and ran on.

I then ran the rest of the trip with the cruise set on 55 and had no unusual events. Overall over the 300 miles all was good except for these two very odd situations.

Any ideas?

Keep in mind I have owned a 2000 Excursion for 14 years and put about 160k miles on it (199k on the odometer) so I am familiar with normal operations of that 7.3L.

Thanks
Gary

 

How full was the fuel tank? I am wondering if the grade and fuel moving in the tank may have starved it (broken foot)? Or maybe a CPS issue? Or a loose connection somewhere?

The fact it happened in a grade both times is what has got me thinking

 

Tank was about half full at the time. I stopped and filled the tank to the top and added a diesel treatment that I could find at the local store. I also wanted to drain the fuel bowl in case of water, but pulling the cable at the front did not result in a puddle. Obviously need to have a really good look at the truck from one end to the other. I know the tank is mounted between the frame rails and seems to hold about 50 gallons.

 

A 50 gallon tank? Must be an aftermarket one if that's the case. The largest stock one is 37 gallons.

What is this cable you pulled to empty the water out of the fuel bowl? It is a yellow lever on the back of the bowl that you turn to do that?

 

Just to clarify. This is an E-450 series Van chassis (not F series) with a ambulance box on the back. Open the hood and you can't even begin to see the fuel filter bowl. There is a cable release for the water drain that is next to the tranny dip stick, but not sure it is connected to anything (in my case).

These are sold from Ford and look like this:
http://cdn.iseecars.com/image2/2043.jpg

I have seen photos where they have a large fuel tank behind the axle, etc. I assume there are several different configurations.

Just learning the differences at this point. For example the E series does not include an intercooler.

 

Just throwing this out there, but did it over boost maybe? I know when boost gets too high the engine light comes on and defuels the engine. The "only up a hill" thing is confusing me.

 

Over boost is a possibility I would guess.

I am used to my other vehicle (excursion with superchips and towing 10k plus weight). Did not really give a second thought to an empty ( albeit heavier) ambulance vehicle. I was mostly using GPS nav on my phone and running cruise.

But once the events happened I limited speed to 55 mph, switched to Torque, and kept an eye on what I could. Boost went up to a max of 12 psi (via the Torque PID's) and HPOP was up to about 3k max. Trans was under 200 F and EOT was about 201 F max. Unfortunately I do not know when the stock ECU would go into overboost nor do I have an EGT installed (yet). Planning on gauge set on A pillar asap.

Certainly both cases were where it was making pretty good power although not at "full throttle". Both were in 3rd gear (downshifted).

 

Over boosts is close to 24 psi, happened to me a few times on my rig. The Boost is not high enough to trigger a code.
The cps is what is really shouting at me, the hill thing is throwing me off.

 

Does the ipr have the tin nut on?

 

Not sure. Will not have a lot of time to give it a good once over for about 8 days. I find it challenging to see anything under the hood. Totally different view then a F-series.

 

My first thoughts went to the CPS and the IPR. One of those is free to check, the other is inexpensive to swap out as a precaution. I then have to ask if the engine sounds "knocky" when under load. If so, one or more loose injectors can make the engine sound more knocky, cause bucking, and pop the SES light because of ICP bleed. A quick look at the fuel filter to see if it's black may point to this.

 

I had a buck/hiccup that was random and sometimes it would throw a code and sometimes it wouldn't. I would try to retrieve the code with Torque Pro and it would only show up sometimes. After finding a bare wire on my IPR harness I replaced the harness and the IPR. I still had the occasional buck/hiccup. I ended up swapping out the CPS (which only had 1000 miles on it) that the dealership had replaced due to a recall with a new CPS from Riffraff and I have not had any issues since. Like Tugly said, its only $25 and an easy part to replace. My vote would be to swap that out after you have checked to make sure that everything looks good with the wiring harness that leads to the IPR and that it still has the nut which holds the solenoid in place.

 

They have you covered here so far. It sounds like a CPS, maybe IPR/tin nut issue, or fuel tank issue, in that order to me. If all of those check out, there may be a bare wire intermittently grounding or a UVCH issue starting to throw it's hat in the ring, but I would look at the first three first.

 

Your symptoms point to something that can cause all of your injectors to shut down, not just a few. So when you are deciding what to check, keep that in mind. A little air in the fuel would not tend to do this, but a lot of air from a tank problem could. A clogged fuel filter or fuel pump loss of pressure would cause exactly this problem, but could idle fine, since fuel consumption at idle is small fraction of what is needed going up a grade. If your oil level is low in the crankcase, the hpop may not be keeping up due to intermittent loss of lpop/or foaming oil, so gauges for this truck will certainly be of value in troubleshooting.
Larry

 

One other thought, vans like this have the metal tanks I believe. The in-tank fuel line screens could be clogged with the tank coating that Ford and after market manufacturers used. A very common problem on this type vehicle. Plastic tanks are the only way to go!