Hello All:

Im posting this for a friend, 99 F350 7.3 turbo. Sometimes right after he starts it up it will shut right off on its own as soon as it runs. It recently started to "hiccup" or stall while driving down the road. The engine will restart instantly and run fine untill it "hiccups" again. Service engine soon light came on but mine and auto zone's code reader could not pull out any codes. After shutting the engine off and re starting the light will go off. Crank pos sensor was recently replaced, could these be related to the problem? The truck has acted up like this on and off for about a year, but now it is getting worse and he is leaving for Florida with the wife and does not want to be stranded with her!!! Fuel injectors and Glow plugs we replaced about 30,000 miles ago and the transmission was rebuilt about 15,000 miles ago. The truck now has about 180,000 on it. Sometimes while driving, the "o/d off" light will flash and speedo stops working, im not sure if these problems are related but its happening also, just wanted to add that too. One last thing, the truck does have an auxillary fuel tank mounted in the bed connected to the fuel system in addition to the trucks own fuel tank.

Thanks in advance!

 

Flashing O/D light = failing VSS (Vehicle Speed Sensor). It's on the rear differential housing. Easy to replace.

When was the last oil change? What type/brand/weight of oil is he using? 7.3 PSD injectors fire off (high) oil pressure, so low oil level, worn out oil, etc. will effect performance.

Does he have a fuel pressure gauge connected so that you could see what is happening at higher RPMs? Dirty/worn injectors could cause you to have low power, but how does the truck idle? If it idles fine and power is good at low RPMs, I'd look at fuel supply/pressure. There could be a clogged fuel filter. Originally there is only the 1 filter on top of the engine, but many people add 2nd filters in to keep fuel clean. Follow your lines back to the tank and make sure you know if you have a second filter or not. It could also be your fuel pump getting worn out. Idle & low RPMs are not placing as high of a demand on the pump, so that could be a cause.

It may not be just one thing either. Even if he finds a dirty secondary filter, check the pump and the fuel pressure to be sure you do a complete fix.

See also THIS THREAD since your issues are so very similar.

 

A lot of the code readers at Auto Zone can't read our codes. Find someone with AE. Is the CPS from the dealer or a parts house? The parts house CPS are not very reliable. Someone here may have a black CPS for you. Try Clay ( RiffRaff Diesel). Did you check the UVCH? It may be loose. If your O/D light is flashing you have a code stored. If the speddo stops it's probably the VSS on top of the rear dif. A real easy fix. When my fuel pump was going out it had similar symptoms. Would fill the fuel bowl, but couldn't keep up with the demand of anything higher than a high idle. Hope this helps.

 

Thanks for the responses guys!

We changed the oil and filter a couple weeks ago and we used 15w-40 Shell Rotella Diesel engine oil. Truck has been driven only about 100 miles since than. When it is running, the truck idles well and is fine at low speed driving. Except when it "hiccups" but that is usually under acceleration or at normal driving speeds. One other note: when it is 50 degrees or colder out, it is very hard to start. He has to turn the key on and off a couple times (cycling the glow plugs) and then crank it before it will start. When it does start, it will blow out black smoke for a few minutes. Where is the Fuel pump located? Is it mounted on the engine, the frame rail or in the tank? We will check the pressure also and change the engine mounted filter and check for another one. What should the fuel pressure be? We heard that the new "low sulfur" diesel fuel can affect pump performance, should he use any kind of fuel system additive because of this? We figured that the o/d light could be that sensor and were gonna get a new one and see what happens.

 

Right after the I posted, he started it up and it fired and stalled again. Cranked it over and was fine. Very strange......

 

Found the inline fuel pump on the frame rail, we're probably going to replace that as a starting point.

 

Let us know what you find out.

 

Heres an update:

Got the fuel pump on order and while he was driving home last night, it stalled and wouldnt restart. He was able to get it started but it was only able to "limp" home. It ran real rough and was missing terribly.

 

That's what my truck did when the fuel pump and CPS went out (at the same time).

 

He was going to change the fuel pump out today, i'll find out how it went on friday.

 

Good news!

I think we got it figured out. We replaced the fuel pump (the one on the frame) and all seems well. It starts and runs like new and hasn't acted up at so far. However, the bracket that the pump was mounted to also had brake lines running through it and it was rusted beyond belief so the brake lines got mangled and we had to replace those also. So far so good....

Thanks for all the help!

 

Good to know. Thanks for the post. This makes me wonder if my truck has a fuel pump that is just now starting to go out as I once had a stall but haven't had once since.

 

Its worth looking into, how many miles are on your truck? His has just over 180K.

 

Mine has 198,000. I know it has an updated starter but that's about it.