Started a motor swap on a 85 M1008, need some electrical advice to get it started

83k30 · Jul 29, 2018

I blew the oil cooler o-rings on my stock M1008 and bought another 6.2 takeout motor from a CUCV out of Ft. Worth, TX. While doing the motor swap I made some modifications to the stock fuel systems. I added an electric Carter rotary fuel pump and deleted the mechanical pump on the block as well as a spin on fuel filter on the firewall. I wired the fuel pump supply from a 12v source on the firewall junction block, through a relay, switched from the 12v terminal on the fuse panel in the cab. When I tested the pump with the key in the run position, the 20 amp fuse popped. Am I possibly overloading the ignition circuit by trying to trip the glow plug relay as well as the relay for the fuel pump with the key in the run position? The other issue I am having before I can start my new motor is with the glow plug relay. With the key in the run position, I hear the relay trip and see the voltmeter indicate a load, but never it unloads...it appears that the glow plugs are cycling as long as the key is left in the run position. Any advice on either would be appreciated.

Thanks

12v source for fuel pump

Green spade is the 12v supply for the relay to the fuel pump, I replaced the blown 20amp with a 25amp

Fuel pump relay

cucvrus · Jul 30, 2018

Hot Rodding and Modification department may be able to help you. Replacing fuses with higher amperage just overloads the wiring on that circuit. Then the entire wire becomes the weak link and melts. Good Luck with your truck.

joshuak · Jul 30, 2018

What 20 amp fuse did you tap into? That may explain the GP system malfunction, have you removed the gp card and checked operation?

Picture is from this thread: https://www.steelsoldiers.com/showthread.php?132309-CUCV-Fuse-Box-Layout

gringeltaube · Jul 30, 2018

cucvrus said:
Hot Rodding and Modification department may be able to help you.......

Thread moved to that section...

nyoffroad · Jul 30, 2018

That extra load on the 20 A fuse really shouldn't have tripped it, I'd replace the fuse with another 20A and see if possibly that old fuse was just 'old'. IIRC there are a couple of 12volt keyed take off terminals in that fuse block, tap one of them and use an inline fuse for the pump relay, the fuse could also be removed as an anti theft device.
As far as the glow plugs, lots of info on here already on how to troublshoot it.

83k30 · Jul 31, 2018

nyoffroad said:
That extra load on the 20 A fuse really shouldn't have tripped it, I'd replace the fuse with another 20A and see if possibly that old fuse was just 'old'. IIRC there are a couple of 12volt keyed take off terminals in that fuse block, tap one of them and use an inline fuse for the pump relay, the fuse could also be removed as an anti theft device.
As far as the glow plugs, lots of info on here already on how to troublshoot it.

Did some testing today, I only have 10.4V coming through the IGN circuit single spade taps...and a new 20amp fuse popped again after double checking my fuel pump relay wiring. Kinda curious why a low voltage input to a relay would pop the IGN fuse. I decided to test the fuel pump isolated away from the keyed 12v and relay. I bought a 50amp switch and tapped the existing fuel pump leads from the relay circuit. Fuel pump worked fine when I bypassed the IGN circuit. I am suspecting that I may have an issue with corroded/loose engine firewall plug, as I remember it being a bit grimey when I had the motor and wire harness out. Also to top off my electrical gremlins my Gen1 light now does not turn on...Any ideas on where to else to look for low voltage in the IGN circuit?

The glow plug issue has been resolved by replacing the pigtail and temp sensor/glow plug inhibitor on the rear #8 cylinder head. Now the glow plugs cycle for about 10 seconds or so before shutting off.

83k30 · Jul 31, 2018

Well I spent some more time looking at it this evening, voltage through the keyed IGN circuit is now 11.8, the Gen1 light is on dimly and Im not sure where to begin looking for issues. The TM shows a .8 PNK/BLK-39 series that seems to power alot of things including the glow plug module, WIF sensor, low coolant module, seatbelt buzzer, cold advance solenoid, voltmeter relay, and the 12V for the IGN circuit and the ENG CONTROL circuit...

I started this motor swap process some weeks ago, with the intent of just bolting the "new" motor in with my original wiring harness and being a plug-n-play. Murphy's Law is sure giving me a lesson in electronics as I first wired the passenger alt wrong and fried three fusible links when hooking my batteries up. After patching the burnt wires, the truck seemed to be ready for fuel and priming, only to find a mysterious short in the 12V side of things....hoping to get this issue narrowed down so I can get my truck back on the road.

Thanks

cucvmule · Aug 2, 2018

Hello 83k30, I have had an 82 K30 6.2 since new and I believe that the spin on primary with water petcock drain on bottom and spin on secondary filters are great additions to the fuel system. I prefer Wix brand but there are others and better systems as well.

In the picture I see an inline fuel filter witch I believe is marginal at best, and also flexible, rubber fuel line. Now to get up and running it may be ok providing that the tank is fairly clean and free of water. The fuel line if rubber may last a year maybe two if it does not flex or vibrate. After a few bits of rubber in the pump, injector pump, problems may arise.

Putting additional load on the in cab fuse box is ok for small amperage devices but I have on other trucks with gasoline engines just wired a separate feed from battery to remote fuse then 20 amp toggle or rocker in cab, depending on function and fuel needs for engine. Also grounding is very important. Truck firewall to engine block, engine block to frame.

Good Luck

83k30 · Aug 2, 2018

cucvmule said:
In the picture I see an inline fuel filter witch I believe is marginal at best, and also flexible, rubber fuel line. Now to get up and running it may be ok providing that the tank is fairly clean and free of water. The fuel line if rubber may last a year maybe two if it does not flex or vibrate. After a few bits of rubber in the pump, injector pump, problems may arise.

I installed an inline filter and spliced into the factory steel lines by cutting them to fit the new hose route. The individual splices are between 12"-18" at most, hopefully I will avoid any other problems.

cucvmule said:
Putting additional load on the in cab fuse box is ok for small amperage devices but I have on other trucks with gasoline engines just wired a separate feed from battery to remote fuse then 20 amp toggle or rocker in cab, depending on function and fuel needs for engine. Also grounding is very important. Truck firewall to engine block, engine block to frame.

I did a quick bypass of the IGN circuit/fuel pump relay and the pump worked fine. I may start the truck with the temp switch installed just to get it fired up for the first time. I still need to hunt down the low voltage issue that is causing fuses to blow.....

Thanks

83k30 · Aug 2, 2018

Well I stopped by to work on my M1008 this afternoon and installed a ground strap from the engine to the cab at the rear of the passenger side cylinder head. Went to the cab to turn the key and begin some voltage checks and got no lights in the dash, no starter engagement...checked voltage at the 12V engine wiring block and had 3.2V. Checked battery #1 and had the same voltage-3.2V. Battery #2 had 12.75. I have been turning my main battery disconnect to OFF in between times when I'm there to work on it, however this last time I did not. It appears that something is drawing current on the 12V side of things and drained my battery, but I have not figured it out yet. Any worthwhile advice is appreciated.

Thanks

cucvmule · Aug 3, 2018

Hello, on your way, grounding, good clean surface on all connections, terminals, check and recheck will be rewarded.

Does the truck still have the firewall pos and neg junction blocks, are they clean. The cables to the front grill, are they chafed at all, grommets in place through bulkheads? Any cables to the bed for radios or any kind of accessories?
Is the column starter key relay hot going out to starter in off position?

First thing I did when I acquired my 1008A1 from the Federal Government was pull the fuse block apart and clean and check contacts, after all water does get through windshield and abuse from wet troopers. When I acquired mine someone was chasing gremlins and in the process burned up 7 new glowplugs. Yet in hot July truck started and loaded fine.

When I got home looked under dash the GPS unit was still under dash and still hot. Wonder how much that is .

I replaced new GP relay with another used one from my 82 K30 and used good glowplugs, cleaned all connections, checked GP card for burning smell, connection. DIRT, SAND, inside of GP card box, wow. Truck is just fine, but did install bypass rocker just in case , do not want to burn up glowplugs. Learned that lesson long ago.

Again a little long winded, Good Luck

cucvmule · Aug 5, 2018

Another thought to narrow down Battery drain would be to pull fuses from fuse box one at a time overnight and check for drain. To eliminate circuits may take time or take cable off each time and see if there is a noticeable spark on connection.

Let me add that really anytime you are around working on batteries that eye protection should be used. Seen one happen close up jumping a truck to a dead car, a very nice explosion. Luckily I was back far enough not to get acid on me and George was looking under fender lip but did burn up shirt pretty fast. Again luckily with quick thinking we had some beverages to pour on Georges skin after shirt came off.

83k30 · Sep 1, 2018

Update

Bought a new group 31 battery for the front battery tray, making 2 new batteries now installed.
Attempted to prime the truck and found a fuel leak
Leak was due to improper size fuel line from filter assembly to injection pump
Ordered correct NPT to hose barb fitting
Waited a week to get back to work on the truck only to find the front battery voltage down to 0.7V
Will charge front battery and persist to find the open battery drain

ke6axc · Sep 1, 2018

One way to find current draws is to take negative cable off and hook test light between post and cable. The bigger the current draw the brighter the lamp will light. Pull fuses one by one, wiggle wire, etc. looking for the light to dim or go out. Found several bad wires over the years this way.

Sent from my LG-LS777 using Tapatalk

Lizard Dog · Sep 3, 2018

ke6axc said:
One way to find current draws is to take negative cable off and hook test light between post and cable. The bigger the current draw the brighter the lamp will light. Pull fuses one by one, wiggle wire, etc. looking for the light to dim or go out. Found several bad wires over the years this way.

^^^^+1

Can do this test with a multi-meter set to Amps DC. Anything more than about 100mA can be considered a parasitic drain.

ke6axc · Sep 3, 2018

Yes. Done that also. I like the light because I can see it from driver seat when pulling fuses or finding bad wire under dash.

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Lizard Dog · Sep 3, 2018

88k30, sounds like your green wire may just be shorting to ground somewhere between the fuse panel and the relay. Have you ruled that out?

83k30 · Jan 11, 2019

Update on my electrical issues. As it turns out when the short occured due to the mis-wiring of the alternators, both alternators fried themselves and tested bad. Bought a few rebuild kits from a SS member and now have correct voltage and no battery drain down. Proceeded to fire up the truck and found the fuel shutoff solenoid is inoperative. Will update when the solenoid arrives. Thanks for the advice from those that posted.

83k30 · Apr 5, 2019

So it's time for an update to this thread. It turned out the IP was seized on the takeout 6.2 that I hauled from Texas. Ordered a rebuilt pump from Oregon Fuel Injection and install went smooth. Truck is now running down the road again. Have a few issues that need to be addressed but I can do that while driving.

So in conclusion, alternators can short and drain your batteries, and "running" takeout motors don't always run. Thanks for the advice to all who replied.

Started a motor swap on a 85 M1008, need some electrical advice to get it started

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