GEM Questions

[white99]

Hey all, I have been building a '79 on a '99 chassis. After troubleshooting electrical problems I have heard they won't run without the GEM. Is this correct? Also I was looking through a Chilton's manual and they show an "Engine control system" (I know it is different than the PCM) what is this? I have relays latching and weird things going on and no GEM. Has anyone ever had a truck that wouldn't turn over or run as a result of a faulty GEM? I previously owned an early '99 f-250 and noticed a module on the trans tunnel, was that the GEM? Thanks

[SCUFFY828]

it is possible to need the entire harness from the 99 to get this vehicle right , the gem des control the 4x4 , and a few other components , whioch means it does read wether its in nuetral ornow, i would think with a little searching and some modifying to the harness you have its possible to get it to spin over and start , the gem is mounted on back of the inside fuse box , i would like to know more about what parts you have used off the 99 model

[white99]

I have the fuse box and did notice there is a printed circuit board inside, is this the gem? If not could it be different on the early 99's? I remember on my old '99 there was something on the trans tunnel, inside the vehicle underneath a plastic cover up against the bottom of the dash, I assumed that was the GEM but I guess I'm wrong? I have used the engine harness, dash harness, steering column, IDM, PCM, fuse box, cluster, I think that about covers it. I did try to jump the starter while having the key on and thought I heard the injectors cycling, I had A LOT of white smoke out the exhaust and no start. The wait to start light cycles like it should so I assumed the PCM is acting properly. I also forgot to mention the fuel pump does not run, I jumped the wires and the fuel pump runs fine, does the PCM control the fuel pump. If not, can I wire the pump and rewire the starter to make it work? If so I will have to rewire the cluster as it does not function, illumination is fine but none of the gauges work.

[white99]

After further review, I do have a GEM. Let me recap: Fuel pump will not run, will not turn over with key, no horn, cluster will not function(except illumination). Wait to start light functions and cycles but glow plugs do nothing. A lot of problems and there is probably one thing causing it all...any ideas?