We have a 99 ford PS in our shop and our we cant figure out whats wrong with. Being the nice guy I am, I am lending my minimally diesel knowledge to our mechanics. Well, actually they don’t know I am posting here.

Anyways, the engine is missing, most noticeably at higher speeds. Scans on the computer say nothing, replaced all fuel filters, the computer, new turbo, and we are currently investigating the wiring around the injectors. Any other suggestions? Trying to be the smart office guy in the shop.

I know they have looked on the PS diesel forums, but I don’t know how computer savvy they are and I think they couldn’t find the exact same symptoms.

 

I'd do a compression check and check the turbo

 

just added that we put a new turbo on

 

What test have you performed?
If you have a good computer scanner you should be able to do a cylinder contribution test. Do at least 2 in a row and see which cylinders it determines are bad/weak.
There are also several other test that deal with injectors that can be done with the scanners. One is the 'buzz' test and the other I mentioned above.

Compression check is a good idea, but won't find a bad unit injector. See if you can perform the test that the good scanners can perform and narrow down to which cylinder it is first.

 

have you looked at the CPS(camshaft position sensor)? those are notorious for weird problems

they are about $70, if I remember correctly

 

also try the fuel pump, how many miles on the truck?

 

Sounds like the same complaint my co-worker had with his '99 last week.
Ran rough, no power, poor economy and NO CODES SET!
They had to take it to a dealer with a programmer and go in and do a cylinder shutdown test and see which one was the culprit. It turned out to be #7 had a bad injector ($285 ea). Also, while they were in there under the valve cover anyway, they changed the wiring harness on that side.. (apparently chafing injector wiring harnesses are a very common trouble point).
New injector and he's all smiles again.

K.

 

Roughly 145K on truck. We have done a cylinder compression test and all cylinders have good pressure. I do not think we have done multiple cylinder contribution tests as decribed above. Whats the best way to determine individual injectors? Unplugging the wire to the injectors make it run very badly. We are currently replacing the injectors wire; relatively cheap and simple.

I would think that a bad sensor would throw a code. Fuel pump is next.

 

I am not sure if you can turn off each injector's wiring or not, but the theory that that is sounds like he is suggesting is much like I use on my race car. You isolate each plug/injector by unpluggin it, (plug wire/injector actuator), if by turning this injector off, the performance of the engine does not get worse, then you have found the cylinder/injector that is having problems...

If the performance gets worse by the isolation, then you know that injector/cylinder was actually working/contributing to the engine runing efficiently..

 

Each cylinder removal makes the engine run horrible; all 8 were very noticeable when removed from service. We changed the wiring and putting it back together now. Miss is barely noticeable at idle, but becomes strong at higher speeds (3 gear +) and has just enough power to move along.

 

if its missing maybe the guy will get lucky and insurance will buy him a brand new dodge with a real motor in it

 

Another vote for teh CPS. Really the only weak link in the 7.3 PowerStroke. They are less than $100 from an International dealer (Ford will charge alot more) and take 10 minutes to replace. When they first start going, it feels like a miss. You are on borrwoed time, when they totally fail, you are stranded.

One wy to check for it is to crank the engine over & watch the tach. If the tach stays at 'zero' it's definately the CPS. But this test only works if teh CPS totally failed.

 

maybe the injector o rings are going out, that also happens from time to time

 

So we have replaced the injector wiring and the problem is still present. As for the CPS, the scanner is showing the CPS is good and inline. Will this fault a code when it is failing or just completely fails?

As for the O-rings and injectors, I would think that the bad o-rings would cause noticeable issues such as oil spewing, etc. We are currently exploring fuel possibilities.

As for the PS, this truck came with a company we acquired. Our CTD is going strong with 250K problem-less miles. (99 or 00).

 

I don't know if it throws a code or not. When it fails you don't have to check codes because the engine will crank, but the tach will be dead still. It's been a part that's been known to fail - alot of guy's keep a spare CPS so they don't get stranded. If it were me, for $100 & 10 minutes of work, I would swap it out. If teh 'miss' does not go away, you will have your spare CPS! If the 'miss' goes away, you saved yourself from being stranded!