1984 m1008 cucv does not start

[Minister956]

• Turn key
• Wait light on
• Gen 1 light on
• Gen 2 light on
• Wait light off
• turn key to start position
• engine cranks
• no start
• GP relay clicks on and off every 3.25 seconds
• wait light off

I got it to start on a warm day and I borrowed my neighbors multimeter and it reads 24v on top of the gp relay from the line off of the resistor pack, a little under 12v at the glow plug then reduces to less than a volt.

Ruben C Ramirez Sr

 

[Crash_AF]

Try two known good batteries, or take yours to an auto parts/battery store and have them tested. I'll bet yours are trash.

Later,
Joe

 

[Minister956]

The batteries are about a year and half.

The engine turns over and sounds good, GP relay is not chattering, just cycling on and off.


Hmmm, stumped.

 

[MakersTeleMark]

Replace your glow plugs and charge your batteries.

 

[doghead]

Test.

Start with reading the -20TM, in the troubleshooting, where it covers, "cranks but does not start".

No point replacing anything until you test.

Fast cycle times often indicates bad GPs.

 

[MarcusOReallyus]

Replace your glow plugs and charge your batteries.

No.

Test.


Replacing parts before testing is the expensive (in time & money) and frustrating way to fix things.

 

[Minister956]

I've downloaded them a couple years ago and frequent them often. I've read "cranks but does not start" I guess what's throwing me off is the 24v I'm reading on top of the GP relay when the truck is on. Shouldn't that drop to 12 volts? CUCV ELECTRIC has a diagram comparison with water pressure that's pretty cool. Yet it still reads 24 volts from the resistor pack when I got the truck to start.

Test.

Start with reading the -20TM, in the troubleshooting, where it covers, "cranks but does not start".

No point replacing anything until you test.

Fast cycle times often indicates bad GPs.

 

[cpf240]

In the stock configuration, ie resistor bypass not in place, the top of the GP solenoid will read 24v when the GP solenoid is not engaged. It should drop down somewhere around 12v when the GP solenoid is engaged and all the glow plugs are working.

Be sure to check what voltage is at the bottom of the GP solenoid when the GP solenoid is engaged. It should be the same as the reading at the top, or *very* close to it. It could be that the GP solenoid is not working properly.

Also be sure to measure the resistance of each glow plug, should be 1 to 2 ohms. If zero or infinite, then that glow plug is probably bad. False reading could come from bad engine ground connections, but I'd say it is usually a bad glow plug.

 

[Crash_AF]

Ok, since there's a lot of chatter here, I'll give you my reasoning and it doesn't matter how old the batteries are.

If your voltage is 24 at the GPR with it open, then you are getting proper voltage from the batteries.
If your voltage is 12 at the glow plugs with the GPR closed, the resistor is doing its job and bringing the voltage down under load, and the glow plugs are all -probably- working.
If your voltage quickly drops to ~1volt at the glow plugs under load, your batteries cannot hold the load, and are the most likely culprit.

Take your batteries and have them tested to be sure, but I'm 95% sure that's your problem.

Later,
Joe

 

[dstang97]

Bypass resistor and check each glow plug. Could be batteries or air in the fuel. Also make sure you have power to the ip

 

[M1008driver]

Make sure you check the battery cables and especially the ground. Probably not, but could be the source of your problem.

 

[Minister956]

these are my readings.



1. Truck ignition off, truck not running.

25.03 A. Voltage at the positive terminal should be approximately 24-25 Volts.
25.03 B. Voltage going into the resistor bank should be approximately 24-25 volts.
25.03 C. Voltage coming out of the resistor bank should be approximately 24-25 volts.
25.03 D. Voltage at the top of the glow plug relay should be approximately 24-25 volts.
00.00 E. Voltage at the bottom of the relay should be Zero volts.


2. Truck Ignition on, truck not running, in glow cycle.


24.7 A. Voltage at the positive terminal should be approximately 22-23 Volts.
24.7 B. Voltage going into the resistor bank should be approximately 22-23 volts.
24.7 C. Voltage coming out of the resistor bank should be approximately 10-13 volts.
24.7 D. Voltage at the top of the glow plug relay should be approximately 10-13 volts.
24.7 E. Voltage at the bottom of the relay should be approximately 10-13 volts.


3. Truck Ignition on, truck not running, not in glow cycle.


24.7 A. Voltage at the positive terminal should be approximately 24-25 Volts.
24.7 B. Voltage going into the resistor bank should be approximately 24-25 volts.
24.7 C. Voltage coming out of the resistor bank should be approximately 24-25 volts.
24.7 D. Voltage at the top of the glow plug relay should be approximately 24-25 volts.
9.69 E. Voltage at the bottom of the relay should be Zero volts.


Left the ignition on for 2:15 seconds still had the 9.69 bottom relay reading i then tried to start it batteries seemed very low.

Ruben C Ramirez Sr

 

[doghead]

Use an ohm meter and test each gp. Your test 2 indicates your GPs are all bad.

How did you determine it was not in glow cycle? Did you remove either small wire from the relay? The light off does not mean the relay is off.

 

[doghead]

GP relay clicks on and off every 3.25 seconds

This is an indication that the GP controller is not sensing a drop in output voltage. Test the GPs.


There is thorough test procedure for all of this in the troubleshooting section of the -20TM. I thought it was immediately proceeding the "cranks but does not start" section.

 

[doghead]

From the troubleshooting section of the -20 TM

c. When troubleshooting a malfunction:

(1) Ensure that both batteries are fully charged.

 

[doghead]

CRANKS BUT WILL NOT START

Step 1. Check to see if there is fuel in tank. Add fuel if empty.

Step 2. Check fuel supply and return lines for restrictions, looseness, or damage.

Tighten or replace if damaged. (See paragraph 3-13 or 3-14)

Step 3. Inspect fuel filter, fuel pump, and injector pump for leakage.

Notify your supervisor if injector pump is leaking. Replace other leaking

components. (See paragraphs 3-10 and 3-17)

Step 4. Check for inoperative glow plugs and glow plug system. (See
Electrical

Troubleshooting malfunction #19)

 

[doghead]

19. ENGINE CRANKS BUT WILL NOT START; ENGINE COLD; “WAIT” LIGHT OPERATES

Step 1. Ensure that key is in “OFF” position. Check for voltage between glow plug relay

terminal where orange lead connects and ground.

If there
IS voltage, replace glow plug relay (see paragraph 4- and perform

step 3.

If there is no voltage, perform step 3.

2-64

MALFUNCTlON


TEST OR INSPECTlON


CORRECTIVE ACTlON


CAUTION


DO NOT leave key in “RUN” position for more than 2 minutes. Failure to


follow this caution may result in damage to glow plugs.


Step 2. Turn key to “RUN” position. Check for voltage between glow plug relay terminal


where orange lead connects and ground.


NOTE


Glow plugs will cycle to 0 volts in approximately 20 seconds after first


operation. Time will shorten as glow plugs become hotter.


If there are 10.0-15.0 volts, ensure that engine is mechanically sound and fuel


system is operating properly,


If there are 22.0-28.0 volts, perform step 3.


If there is no voltage, perform step 4.


Step 3. Disconnect each glow plug lead and check for resistance between glow plug terminal


and ground. Resistance should be 1-3 ohms. Check glow plugs for looseness or


damage.


If any glow plug does not have correct resistance or is damaged, replace, (See


paragraph 3-20) Tighten any loose glow plugs.


Step 4. Tag and disconnect all glow plug leads from glow plugs. Check for voltage between


glow plug relay terminal where red lead connects and ground.


If voltage is 10.0-15.0 volts, connect glow plug leads and start engine.


If voltage is 22,0-28.0 volts, perform step 5.


If there is no voltage, trace circuit back to positive terminal board. (See wiring


diagram F-7 or F-


Change

 

[doghead]

Resistor may be hot. Use care when performing this step or injury to

personnel may occur.

Step 5.

Step 6.

Step 7.

Step 8.

Disconnect batteries, pull out bracket and resistor assembly (see paragraph 4-44,

REMOVAL, step 4), disconnect output (red wire) from relay, disconnect input (blue

wire) from input to resistors. Connect positive lead of multimeter to blue wire;

connect negative lead to red wire. Check resistance between resistors and ground.

Resistance should be 0.28 ohms.

If resistance is not correct, replace resistor, connect glow plug leads and

perform step 6.

If resistance is correct, connect glow plug leads and perform step 6.

Check for voltage between glow plug relay terminal where pink/black lead connects

and ground.

If there is voltage, perform step 7.

If there is no voltage, trace circuit. (See wiring diagram F-7 or F-

Check for voltage between glow plug relay terminal where light blue lead connects

and ground.

If there is voltage, perform step 8.

If there is no voltage, replace glow plug relay. (See paragraph 4-

Check for voltage at light blue lead on glow plug module.

If there is no voltage, trace circuit (See wiring diagram F-7 or F-

If there is voltage, perform
Electrical Troubleshooting malfunction #15.

2-65.0/(

 

[doghead]

The above posts are directly out of the -20TM troubleshooting section.

Please follow them and tell us if you do not solve your problem.

 

[Minister956]

Done that.

CRANKS BUT WILL NOT START

Step 1. Check to see if there is fuel in tank. Add fuel if empty.

Step 2. Check fuel supply and return lines for restrictions, looseness, or damage.

Tighten or replace if damaged. (See paragraph 3-13 or 3-14)

Step 3. Inspect fuel filter, fuel pump, and injector pump for leakage.

Notify your supervisor if injector pump is leaking. Replace other leaking

components. (See paragraphs 3-10 and 3-17)

Step 4. Check for inoperative glow plugs and glow plug system. (See
Electrical

Troubleshooting malfunction #19)