Loss of Power

[DKeen]

Here we go again guys. Need a little guidance. 1996 with only 78,000 miles. I am on my third injection pump. Here is the diagnosis.

When the truck gets hot and is under load- pulling trailer or going up a grade, I loose complete power. I can put the pedal to the floor but seems that I am not getting fuel to the motor. A pump test says that I have 5-6 lbs. when when running normal. I have new lift pump (about a year). What else could be the problems: PMD, OPS - I am going nuts, again.

[JohnC]

Without the DTC codes any guessing would be just that - guessing. Get the codes read!

[DKeen]

That is the problem. I am not getting any codes.

[JohnC]

That is the problem. I am not getting any codes.

Are you sure? Did you check them?

If no codes, change the fuel filter, air filter, etc....

[DKeen]

Yes- I put the ODB II reader on it. I did some research on the forums and found some old threads that stated if the EGT or AIT (air intake temp?) got to high the ECU would shut the fuel rate down.

Would this occur without a code? Where are the sensors for these?

Would a #9 resistor or a ECU upgrade take care of this?

I have replaced lift pumps, OPS, FSD and injector pumps. I will change the fuel filter and clean the air filter (I have SS cold air intake system). Any further guidance would be appreciated.

[JohnC]

I can put the pedal to the floor but seems that I am not getting fuel to the motor.

You need to supply a little more detail here. Does it slide backwards down hills, or is it just not quite as fast as you want it to be?

The answer may to put a scanner on it and see what's going on when it happens.

The PCM will reduce the fuel rate if the IAT or boost pressure are too high, but I wouldn't describe it as "fuel not getting to the [engine]." Also, if the cooling fan kicks in, this pulls a lot of power.

[DKeen]

John- I am not sure how else to describe it. I can put the peddle to the floor and nothing happens- no down shift,no powe,r no motor change.

When it does start, it continues even without a load or stain on it. If I pull out of stop sign and put it to the floor the rpms will raise but not to the point that the truck wants to shift to the next gear and it has no power or pull.

I am in VA and I am not talking about STEEP grades here. I bought the truck new in 1996 and this problem has come and gone for the past two-three years. Nothing seems to resolve it- new lift pump, injection pump, FSD's. The reason I described it as "the motor is not getting enough fuel" is that was the best way for me to describe it. Almost like the filter was clogged or maybe a fuel line plugged. Gets enough fuel to run but not enough to pull full strenght. Sorry, I can't seem to come up with a better way to describe it. In the past I have gotten a PO236 code (boost ref. function) but I have not gotten that recently.

[JohnC]

I think you need to put a scanner on it and record the data stream. the symptoms you describe SHOULD set codes. Something isn't making sense.

[sailun]

I noticed you mentioned "no down shift".

I don't know diddly about these things, but.......

Do you have these problems only when your air conditioning is on ? If I'm on the highway, quite often my Burb will not downshift when the air conditioning is on, I've learned to hit the button when I need more power.

I've always assumed it's a programming error, but maybe it's one of those voltage or ground problems we read so much about.

FWIW