'03 with starting problems

[JHenry]

My son has an '03 with 150000 miles. He has had intermittent starting problems for a couple of years. We live in Idaho where normal winters require plugging the truck's block heater in most every night. When he does, the truck ALWAYS starts.

In spring or fall, the temps frequently drop to 40 or lower. When this happens, the truck won't start unless he plugs in the block heater.

The engine cylces normally when it starts while it's warming up, which indicates to me that the warm up heater is working.

The mechanic who tried troubleshooting said both heaters seem to be working.

He determined that the lift pump was weak and replaced it with a new one.

This didn't help the problem, which still continues.

The truck runs strong, performs well, and shows no signs of excessive smoke.

He has made no modifications to the engine other than a Banks muffler.

Any suggestions?

Thanks. JH

 

[Slow Six]

There has been a lot of discussion about this. I had the problem and the fix for mine was new injectors and crossover tubes. The ECM needs a minimum pressure on the rail before it will fire the injectors. Faulty injectors or a leaking crossover tube is all that is needed to create a low pressure situation. There may also be other causes, but this has been a common one for a lot of us. If you do a search on here you will find a lot of info.

 

[JHenry]

There has been a lot of discussion about this. I had the problem and the fix for mine was new injectors and crossover tubes. The ECM needs a minimum pressure on the rail before it will fire the injectors. Faulty injectors or a leaking crossover tube is all that is needed to create a low pressure situation. There may also be other causes, but this has been a common one for a lot of us. If you do a search on here you will find a lot of info.

The pressure was an issue until the lift pump was replaced. Now there is sufficient pressure. What we don't understand, is why does plugging in the block heater improve the problem?

 

[JHenry]

The lift pump supplies the CP3 injection pump. The CP3 supplies the fuel rail. If the injector bodies or tubes leak, you may have a fuel pressure problem there (beyond the lift pump).



I have an '03 and '06. The '06 is a daily driver. I see you have one as well. As you know, the '06 should start without benefit of the heater grid down to 10 degrees - hop in, it cranks and it starts, perhaps a bit of smoke but should idle smooth after a couple of seconds. Perhaps 0 or 20 degrees, anyway you probably don't need to wait for the heater grids, much less plug it in.



Since you have an '06, try starting his '03. Does it crank fast? Is it the original battery?

The engine cranks and starts perfectly above the 40 degree range. This is what is confusing to me. Why would plugging the block heater make it start? I have been wondering if the grid heater is not working.

 

[MMoroney]

Plugging in the block heater will warm the oil a little bit, plus with other parts of the engine warm from the heated coolant, the starter can spin the motor over easier at a slightly higher rpm. The higher RPM will increase rail pressure allowing the injectors to work. I would perform an injector return flow test at this point.



Mike