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GMC P3500 with GMC B 3.9L/4BT 5 speed manual

5K views 9 replies 5 participants last post by  lmgmcp3500 
#1 · (Edited)
I Just bought a 1993 GMC P 3500 step van. What should I know about general maintenance and upkeep. I have never owned a Vehicle with a diesel engine

before. I had Intermittent problems with power bringing it home over a 500 mile stretch. Some times it would barely do 45 MPH up a slight incline and

other times it would go 60 up a steeper hill. What is causing that? The guy that I bought it from, said that it had 105 horse power and that it got

17MPG. The Engine is a B3.9L/4BT engine with a 4 speed plus low and rear manual and an inter-cooled turbo on it.Engine Data Tag says it was made in 93'

and I think the numbers on the tag are 921918 Is it possible to give it more HP or Torque and/or fuel mileage? Also, how often should the air/fuel and

oil filters and oil be changed. Is there anything else that should be tuned up. Any help or suggestions would be welcome. Thanks
Luis
 
#2 · (Edited)
The 4BTA (A means aftercooler) those are rated at 120hp. So if you get an intercoole/aftercooler you may get power out of it. Oil should be changed roughly every 5,000 miles. If its black you change it. Air filters are around 12,000 miles unless you live and drive on a dirt/gravel roads then its more often. From what I have been told a K&N Air filters let more particles in through the engine so going with paper filters may be better.

Oil changes are around 7500 miles. If you run an Amsoil bypass with 2 filters it may go to 15,000 miles.
 
#4 ·
Most diesel syn's (rotella etc) will blacken after the first 150-300 miles as the new detergents begin to work. While these deteregents are not exhausted from doing their job for another few thousand miles... the color change occurs almost immediately... (a couple engine hours)

Change your oil accordingly to your use and the size of your oil pan. 6BT's with 15 qt pans..... 8-10k on light duty use..... 4BT w/ a small modified oil pan .... every 3-5k
 
#6 ·
First off, welcome to the forum. To know more about your engine I would suggest you go to Cummins Quick Serve on line and set up an account. The basic service is free. Enter your 8 digit engine serial number (ESN) off the ID tag and you can find out every part in your engine and it's specs. If it was ever rebuilt by Cummins it will tell you that as well.

Your varying power problem could come from a number of sources and is kind of hard to trouble shoot. It could be a weak injection pump or combination of other factors. Two gauges you probably don't have on a step van are turbo boost and pyrometer. They can tell you a lot about how the engine is running. Another that is very helpful is fuel pressure from the lift pump. The lift pump on these engines that feeds the injection pump is not know to be the world's best. It's a simple item to replace and not very expensive.

As far as adding performace you have tons of options. If you are getting 17mpg I wouldn't expect that to improve by worlds because you are driving a heavy vehicle with the aerodynamics of a cement block. The gas version of that van probably got half that. There are a number of tweeks to the injection pump that will cost you only the time of doing them. One problem with these engines is you don't always know just how many miles it has on it. After the lift pump, one of the first items on the list might be to have the injectors checked. Find a reputable diesel shop in your area, remove the injectors and have them pop tested. It won't cost a fortune and will eliminate that problem. If they are bad you can either have them rebuilt or replace them. Another item to check is the turbo. Look for any oil in the compressor housing or exessive side to side or end to end movement in the compressor wheel. This would mean a worn turbo in need of rebuild or replacement. Rebuild kits are cheap and this is something you can do yourself if you have the tools and the skill. Complete service manuals can be found on Holset's web site for free. If you're not sure when the engine was last serviced I'd change the oil and filter and the fuel filter. When you do that one be sure to fill the filter with clean fuel before you install it. Air in the fuel system can be a real headache.

Since this is you first diesel you will find they are a different animal. Diesels are known to produce their power at lower rpm's than their gas cousins. The peak torque on your 4bt come in around 1700 rpm and peak HP at 2500 rpm. The engine has a governor that prevents it from reving too fast as you have probably already found out. Although you can change the governor limit it is good to learn how to drive within the engines specs. Take your time and look around the forum. There is ton's of valuable and free info here. An again welcome.
 
#8 ·
ULSD won't hurt anything. Though just heard the EPA is going for even stronger emissions on Diesel engines and ULSD so there maybe problems in the future so stay sharp.
 
#9 ·
I realized when taking off the pipe that comes from the turbo, to the intercooler on my 4bt engine that there was black oil in the pipe. Is that unusual? I was wondering after watching some videos on YouTube, if maybe some of the seals in the turbo maybe leaking oil. I also noticed (while driving a few days ago) that I seamed to have no power and didnt hear the quiet whistle of the turbo and then a few min later I heard it and seamed to have more power. Haven't had a chance to do much checking into it yet. Thanks for any help or advice you can give.
 
#10 ·
Text Font Water Photography Number

do these numbers make any sense to any one. I also found a line of numbers on the fuel pump side of the engine block that was 9 didgets long. I'm having a horrable time finding the ESN on my engine. Could Several people please post some picts of what there ESN tag looks like so that i would give me some idea of what to look for. thanks. Luis
 
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