Hey guys, my first post on the forum, I don't see a beer icon so I'll buy everyone a round of to start out.

I bought my first diesel a couple of weeks ago, a 89' D250 with the Cummins 5.9. I'm planning on just using this truck to haul equipment, pull the boat etc, etc. I'm not looking for performance, just reliability, decent fuel economy and the ability to pull 3,000-8,000lbs every once in a while.

So far I replaced the injectors, changed oil and filter and air filter. I noticed that the oil light comes on when I first start up the truck, that and the pressure gauge only goes up to the second line. I checked the oil pressure at the filter and got 25lbs at idle, sounded ok to me, bad gauge right?

Something else, the truck will stall after I slow down at a stoplight, the oil light will come one and it dies.

Another thing, I would really like to see more top speed. WFO is about 75mph, what do you guys suggest? Going to a 3.55?

Thanks for any input you may have!

 

My oil pressure does same thing on first start. I have replaced sending unit though, which is often the culprit.

Does the oil light come on before or after it dies? If after, that just means the engine died. You may need to turn up the idle.

Is your truck an auto? If so, it has a 3.08 and going to 3.55 will lower your top speed. If it is a stick and happens to have 4.10s, it will help to switch.

Welcome to DTR btw!!!

 

Allright, thanks for your response.

I believe the oil light comes on right before it dies, I'm not 100% sure though.

It seems like it dies easier going in reverse.

It is the auto tranny...

I will try turning up the idle and let you know how that worked.

 

Ya my truck dies in reverse easier too. Mine idles fine when cool, but when engine and air is warm it starts dying, after a/c has been run.

 

The oil light/low gauge reading is due to a faulty sender. Get a new one from Cummins or Dodge (don't get the aftermarket garbage).

On the dying at lights issue - as was said, it's idling too slow. The low speed idle screw is easy to find but hard to reach. A bent wrench makes the adjustment easier, take a look in the technical photo gallery for an example. If it only does it when hot, start saving for a pump. It's only a matter of time.

Top speed sounds pretty good for a stock '89 auto. Back out the high speed screw all the way and put in a 3200 RPM spring. Then your speed will be limited by your fuel budget.

 

Thank you Dave, couple of questions for you.

You said I have a pump going bad, do you mean the fuel pump or the injection pump?

I've read in the past that putting in new springs will increase my top speed by increasing the rpm's. What is the max rpm's right now? If I put my foot to the floor I get about 75mph, is this bad for the truck?

Thanks!

 

I'm guessing injection pump ($600-700) over lift pump ($35.99) since he mentioned "start saving" also...

While the price might sound bad, when you consider the 2nd Gen IPs can easily triple that price and PS injectors are $450 EACH... the 1st Gens are the most economical to maintain...

 

If the slow idle is only on a hot engine, the injection pump is getting worn out. Eventually it will not want to start when hot, that's when it's time to replace it.

If the truck is set up stock, max RPM will be around 2600. Won't hurt it a bit to run like that all day.

 

Ok, that's not good news but it's ok...

Good to hear that 2,600 is the max. I was tempted to run it on the highway maxed out but wanted to check here first...

 

Biggator, since we are driving about the same truck, please post your fuel mileage when you get a chance. Welcome aboard.

 

You can run 3000-3300RPM all day and not hurt anything but your wallet at the filling station. I have just heard this and have not verified it for myself, but valves start to float at the 35-3600rapm range. Stay a good deal shy of there and you should be fine.

Might look into an OD- either a stock-ish (with upgraded internals) 518 or a Gear Vendors/ USGear overdrive unit.

 

Searcher, I will be happy to. The truck doesn't get driven much but I'll IM you as soon as I calculate them.

Overdrive would be a good idea, I'm sure it's something I couldn't install but I might look into having a shop do it.