I have a 7.5L in a Coachmen RV that has not been run for many years. I finally got it to start and idle by replacing fuel pump, MAP, idle air control and TPS.
The EEC-IV test finally shows no errors but the engine has very little power when cold and completely stalls when it warms up if climbing the slightest hill.

Fuel pressure reads 50 at idle and down to 42 when full throttle (tested static).

Seems to be running rich, black smoke when trying to climb hills.

I haven't checked the timing but this engine only has 34,500 miles and likely has not had any work done to it.

Any thoughts would be most appreciated.

 

If it has set for a long period of time and you did not add in fresh fuel, , stale fuel will contaminate the spark plugs and present all types of running problems.

Did you do anything regarding the old fuel and checked the condition of the plugs?

 

I changed the fuel pump and cleaned out all the old fuel while I was there. I have pulled a couple of plugs just to see their condition and they look normal for 34,500 miles.

 

Additional info:
I checked for leaks using propane but didn't see any increase in idle speed but then the engine died as it was approaching running temp. I tried restarting and it is backfiring through the intake.

 

When was the ign coil replaced?

Going just by mileage to replace plugs is not reliable especially if the engine has idled a lot.

 

I have just bought this RV so no idea if anything has been changed in it. It's nearly impossible to see the timing tab because of the access to the engine is from the dog house and the fan shroud is in that way. I'm going to see if I can make some timing marks that correspond to TDC and 10 degrees before to see if I can determine if the timing is accurate.

 

What you are planning will not do any harm, but I do not believe timing will produce the over rich condition that was reported.

You might pull the vacuum line off the fuel pressure regulator and see if any gasoline comes out. None should come out.
What seems inconsistent is, The black smoke and yet the plugs don't show any sighs of over rich mixture.

 

As inaccurate as this investigation was it seems that the timing is very close to being right on 10 d BTC. I changed the fuel pres. reg. a couple of days ago and I'm now in the process of trying to get the EGR valve off (lots of rust to soften) I'm hoping to find it stuck