Recently, coincidentally after changing the water pump, my 1996 7.3L started bucking like it was missing while warming up. I went and drove it and the problem went away. Today, I was warming it up in 55 degree sunny weather, and I heard it start sounding like it was missing. It got louder and missed even more, sounding like it was slowing down. Then it died.

I tried to restart with no luck. Brand new batteries today. I get puffs of white smoke after a few cranks. It sounds like it wants to fire, but won't. I have enough oil, the high pressure pump in the front is full of oil, kinda dark and thick though.

I have had a post a week or two ago about a weird cold start problem where as it would just crank and crank until there was a heavy clunk (not a relay movement) under the hood. Then it would fire up immediately.

I doubt it is a GPR problem as it was already running and warming up.

Any suggestions? I would sure appreciate any input.

Thank you.

 

I also did another check. I pulled the filter and cranked. If fuel were supposed to come from the 1/4" hole near the top on the drivers side, nothing came out. However, some bubbles from the bottom of the filter holder and the level did rise.

 

The hole on top goes to the regulator....that's an exit point.

The smoke while cranking and rising level in the bowl suggest the fuel pump is pumping....and that the cam sensor is good.

At this point if I were going to guess I'd say maybe the IDM, but that does not, nor can I explain, the loud clunk.

 

Hi All,

I checked the codes with the key in the on position. Not sure if that is correct, but it came up with P0603 PCM. A posting states, "0603 PCM Powertrain Control Module KAM test No historical faults output during self test Open PCM pin, disconnected B+, faulty PCM".

Can someone tell me what that means and what I may do to fix it?

Thanks for your input!

 

Do you have a programmer or chip in your truck? That code says you do, and dont worry about it. The chip or programmer overwrrites the stock programming with its own.

 

I did have it programmed for years in the tow zone. I had programmed it back to stock prior to the code reading. I think I will clear the codes and start cranking again, then check the codes. I am so stumped here.

 

I cleared the codes and cranked again. I verified the gpr worked fine. I only got a P1111, no problems! Go figure. It just wants to start and tries to fire, but no continuance without the starter going.

Guess what happened during one cycle on/off with the key. It just cranked, no desire to fire... I thought that is weird now... but alas, the CLUNK. I knew my old friend was back for the cold mornings. After the clunk, it was back to trying to fire like prior. This fantom clunk seems to come from down low. Could a stuck BPValve be that clunk or the sensor for it?

Thanks!

 

Just a stab in the dark here...but have you checked to make sure your starter bendix is good, the starter is turning over fast enough, and that your ring gear has not broken loose.

Do you have a after market oil gauge? If so are building any measure while cranking?

The only things that I can think of down low are: starter, ring gear/flywheel/felxpalte, crank, main bearings, rod bearings.

 

Starter is good, no after market, but during cranking the dash shows oil pressure. I am going to change the oil and see if anything changes.

 

I changed the oil, including the HP reservior, with some Amsoil. Changed the fuel and oil filter. Cranked abit, acted the same, saw my oil pressure register. Gave it a break for 5 minutes, prayed, and she fired up. Runs perfect!

It is amazing how, even though the oil was full in both tanks, it must have been too thick. I am glad I switched oils. Now, if I can just figure out that clunk!

I think it is the back pressure valve sensor. I think it is malfunctioning and staying shut on cold days. I think I hear it slamming open or shut. Does anyone know where this little fellow hides?

I learned one thing. If it all of a sudden won't start or sounds loud then shut down. You must check the oil condition and level!

Thanks all for your help!