Possible bad ECM?

[jonflies]

Have been adding and upgrading, getting ready to pull a travel trailer. My 99 burb with towing package, has 199K highway miles. I had the timing chain and gears changed last year to tighten things up, and this IP only has 90K on it. Had a new rad, vacuum pump and some sheet metal replaced due to a wreck last year.

I've added 4-inch exhaust, new injectors in the last couple of weeks and my last pmd/fsd was put on last October. I had it on a cooler, laying under the floor vent in the cab. I have made sure that the fan was always on, and it had priority to the AC over the humans.

Had a no-start condition last week, while the engine was warmed up, so I bought a new pmd/fsd. Still no start. disconnected the extension cable and went direct to the original cable and the truck started.

Figured I had the issue licked until Wednesday, when I had the same thing happen. One of the last things I did before I finally got it started was to disconnected and reconnected all of the connectors on the ECM.

It was recommended by one guy that the pmd harness could be bad, so I bought one and installed it today. (While doing that work, I found an AC pressure fitting cap wedged in the number one intake port on the block. There was some worn spots but other than that I was able to fish it out intact.) Truck started three times, even when warm, so I figured I had the issue fixed again.

Went out to take a drive an hour later and no start. Checked for fuel at the injectors (as usual) and checked for codes. Disconnected and reconnected the ECM and it started after two full seconds of cranking.

Could it be a bad ECM? I've searched the forum and have not found more than a couple of references to the ECM on the 6.5 side.

[racer55]

I would start with checking the operation of the fuel shut off solenoid,.
Get the easy stuff confirmed functional first.

[racer55]

Is your PMD mounted on a heatsink and do you have a resistor installed?

Also is the ecm B fuse making good clean contact?

How about the ignition switch,does your dash work properly when the no start condition exists?

[jonflies]

Yes, I have the pmd mounted to a "Beta" cooler, now bolted to the intake, connected using the stock-length harness.

Not sure what the B fuse for the ECM is.

The dash is normal during start attempt.

I've got a fuel shut off solenoid arriving today.

I'm changing the MAP and connector, IAT, temp switch and sensor today as well.

[racer55]

When using an intake mounted heatsink the general rule is to move the PMD harness/fuel solenoid ground to the heatsink in order for the harness to reach the new location-this is a bad idea.

The anodizing on the heatsink is an electrical insulator and you must rely on that ground to open and close the fuel solenoid.

If your setup is currently as described you would be well advised to get a PMD extension harness and move the PMD/heatsink/resistor combo to a location outside the engine bay(behind or under the frt bumper is common)and put the ground wire back to its original position on the top of the IP.

If that is not what you want to do at the present time,extend the ground wire I spoke of with solder and heatshrink and piece of wire so that you can return it to the optical sensor screw on top of the IP where it belongs.

This is speculation on my part since you did not post a picture of your heatsink setup.

[jonflies]

I left the ground where it was, on top of the pump. In the past, I had a long extension and had the pmd on a cooler laying under the AC floor vent, and that worked for at least 5 years without a problem.

[jonflies]

Changed the Fuel Shut off solenoid and put larger battery cables (2-0 to starter and crossover). Changed MAP sensor connector, optical sensor connector, temp sensor and temp switch, IAT sensor, OPS, just to rule out bad readings. Spins like crazy but still doesn't start when warm/hot.

I'm thinking it is the IP, since I've been told lift 3-PSI pump pressure shouldn't matter on start. Can somebody with knowledge confirm or deny?

[DaveBr]

Put a couple of quarts of oil in your tank and fill it with diesel. This will change the viscosity of the diesel and if your truck starts when it's warm you will know that your IP is done. The fuel is bypassing the pump plungers.

[racer55]

Put a couple of quarts of oil in your tank and fill it with diesel. This will change the viscosity of the diesel and if your truck starts when it's warm you will know that your IP is done. The fuel is bypassing the pump plungers.
That is an idea for the memory banks!

[DmaxMaverick]

Pouring cold water on the IP is a solid indicator, too. It cools (shrinks) the housing, before the inerds. If it starts, the pump is worn out.

[jonflies]

Thought I'd give an update for those who care and for those who might run into this in the future.

I changed out the Injection Pump and no more hot starting problems. Fires up right away. It makes sense that the old IP was able to pump and crack the old injectors, but the new injectors probably have a higher cracking pressure, and when the fuel is thinned out and the pump expanded due to being hot, less pressure was generated to pop the injectors.

Simply checking for fuel source (looking for fuel from the lift pump by cracking open the line at the IP) or cracking open the IP lines at the injectors only indicated that fuel was present, but not necessarily at the right pressure to pop the injectors.

After all the updates I sense that I do have more power, as I only had one down shift the whole trip up to the mountains (albeit small mountains in North GA) but my mileage remains the same, about 19 MPG empty and 9 pulling my 26-foot camper.