E99 and the GEMs....could be the name of a band.

E99 F250 Lariat, 7.3, ESOF 4x4, ext-cab, manual transmission. 184k miles. June 1998 build date.

In the process of dealing with the fabled electrical gremlins (random horn, chimes, door lights, etc), in addition to a non-functioning 4x4. To deal with the gremlins, I pulled the fuse-box, took apart and deep cleaned the bus-bars, put it back together. Aside from some connecters not providing continuity from fuse tab to the bars initially, this went pretty well and took care of the randoms. No joy on the 4x4 though.

Focusing on 4x4, checked power/continuity from switch to GEM to relays to transfer case motor. After all was said and done, no signal from GEM to relay to cause it to make contact and power the case motor. No problem, this is a common symptom of a problematic GEM. Aside from non working power windows (after the fuse box cleaning) and the relay delay issue (ongoing for the 5.5 yrs I have owned it), truck runs OK with the current GEM.

Ordered a "new" GEM from Ford (yikes these are getting up there). Installed the new one today after starting/running the truck for 1 hr with the existing GEM (here in Maine, wanted to get everything warm). No start. Usual lights, cranks, but nothing coming out of the exhaust. Tried several times - no luck. Checked the level in the HPOP reservoir and it was topped off (sometimes this drains and causes a crank no start). On the last crank I noticed the fuel gauge wavering around.

Removed the "new" GEM and reinstalled the old GEM. Same thing now - No start. Usual lights, cranks, but nothing coming out of the exhaust.On the last crank I noticed the fuel gauge wavering around. In other words the no start is the same with "new" and old GEM now. Thinking that I may have disturbed a wire in/out of GEM, I examined the 2 plugs. Nothing obvious, but cannot rule this out yet. Checked fuel pump fuses/relays and they are OK.

Checking the GEM plug diagram, there really isn't anything there that would instantly cause the crank/no-start condition, aside from the brake pedal position (?). With manual trans, the brake doesn't come into the picture on start.

New Denso starter, new Adrenaline HPOP,new Melling LPOP, and new OEM fuel bowl assy within the past 500 miles. These really upped the cold weather start game. Batteries good.

A couple of questions:

1. Could putting in this new GEM somehow interacted with PCM and negatively impacted something? Changed programming, or tried to? Note that changed my PCM from a 402 to 422 (I think) several years ago with no troubles experienced since.
2. My truck only uses 2 of the 3 plugs into the GEM - always has it looks like since I cannot see any indicator a third wire bundle ever existed. The middle plug is not used. Any possibility here? I don't think so, but one never knows.
3. If/when I get this resolved, does anyone know for sure whether the new GEM needs to be programmed at the dealer to match the truck? I do not have key fobs or remote entry FWIW.

Thanks in advance!

 

I feel like GEM is not the reason for no-start.

Can you buzz test, pull codes, etc?

 

I agree. The GEM has no direct interaction with PCM as far as I could tell. Plus the fact it isn't starting whether the new one or old one is in there points elsewhere.
No codes yet, but should have something tomorrow when I can get back to the truck. I was able to confirm no signal from PCM to glow plugs and fuel pump relays before I took off. A possiblity is that when I disconnected/connected the batts something happened and fried the PCM. I have a spare PCM, but I want to make sure I understand what went down so that I don't fry that one. I use knife switches on my batteries as disconnects. That set up has never caused me any problems.

 

Start with fuses. I LOVE my power probe for this job. Fast and easy and tests the circuits that are grounded as well as 5 & 12 volts.

 

I have seen those around. I may just spring for one.

Of all the electrical troubleshooting I have done on this rig, I can say I have only measured one active voltage from the pcm/idm/gem and that was figuring out my first bad glow plugs relay. I cant recall what I measured. Every other time it has been confirming no signal, therefore no voltage. So when you mention 12/5 volts on that power probe, are you saying that the voltage signal from the pcm (or idm or gem for that matter) is 0-5 volts? Makes sense from a "computer" standpoint, but I can't say I have read that anywhere.

By the way, I continuity tested all the fuses in the PowDistBox. They were all good. PCM fuse inside was good also.

 

When you purchase the Power Probe....do yourself a favor and do the power probe THREE....its worth the extra money over the "regular" Power Probe Two....THE FACT THAT IT HAS THE MULTIMETER SCREEN IT IT IS GOLDEN etc....even for a DIY guy the one time you need to use it for functions the TWO doesnt allow...it would be worth the extra expense....our trucks are complex enough that you will have the insurance to know that you have the tool that can do it ALL...It will quickly become your GO TO TOOL for anything circuit etc electrical diagnostic.A power probe 4 would be good for someone who does large truck since they can test 48 volt circuits and remotely BENCH test things like the starter...quite a nice tool but unless your using it regularly and for that type of thing...its big bucks where most of the big buck features wont ever be used....a Power Probe 3 OVER the PowerProbe 2 is suggested by MYTOOLMAN....

 

Good call. I had a ‘2’ a loooong time ago. I thought it was awesome. Got a ‘3’ when they came out and never looked back.

I only paid $50 for my last ‘3’.

The ‘2’ is only slightly better than a test light. ‘3’ Is a ridiculously useful tool.

 

thanx for the verification/confirmation of facts and opinion given..mytoolman will ONLY steer you in the best diection!

Me and \"Ethyl"*THE*ToolTruck(ETTT) she is sporting her as she left Henry's Dearborn Plant in 1955 drive train...time capsule back to 1955.