Electrical Problem on GMPD4106 (Success!!!)

[luvrbus]

Fred,check the amp draw at the starter Uni-T makes a nice affordable clamp on meter for AC/DC sales for around $40.00.
Check the amp draw cold it should be around 500 amps cold ,then check it hot if the meter shoots off the scale you possibly could have a problem try that first.Making 4/0 cables is a expensive way to do a test 

[Utahclaimjumper]

  Fred,,as I indicated, run a line from the point that you attached starter ground to the block directly to the battery bank ground..
 Without this ground run you are depending on the ground straps from the engine to the chassis, and they don't do a good job.>>>Dan (Many have been removed over the years)

[Fred Mc]

Thanks Dan. I now have a cable from starter negative to the block and to the battery. Im still really confused as to how it all worked previously without a ground from starter to block.
.

[Utahclaimjumper]

 Fred, did you solve the HOT start problem??>>>D

[Fred Mc]

Still haven't solved it. I put on a second set of cables last night.So I now have 2 positive and 2 negative cables that go directly from the batteries to the starter.I also have a ground strap from the starter to the block. The batteries (3 900 cca) are new and the starter just rebuilt. When cold the motor spins really fast and starts quickly.When hot its like the lights were left on overnight and the battery is low. Starter will engage but thats about it.

[Lee Bradley]

We used a 6-71 to power our sawmill and one day it would not start hot. Same thing cables, batteries, starters. Finally found gasoline in the diesel; tanker had used a gasoline compartment for diesel and still had some gasoline in the compartment. Finally got it back on straight diesel and the hot start problem went away.

[Charles Seaton]

1970 GM T8H5306A, eight-cylinder fishbowl transit with VS2-8.  Same issue.  Started cold but does not appear have enough juice going to starter to restart a hot engine.  Not uncommon with this set-up.  I lived with it until bus was sold several years ago.

- Seaton

[Fred Mc]

Thanks Charles.
That doesn't sound encouraging.
Had a reply from Delco Remy and they suggested that it may be a hydro lock from fuel or coolant in cylinder  but i dont think either would flow in that fast after shutdown.( I turn it off and immediately try and restart)
Haven't been able to find a clamp on DC gauge to measure starter draw.

[luvrbus]

A 4106 usually don't give problems starting hot ? is that the same starter that has been on the bus for years.

Do this get the engine hot and try the starter if it won't turn over take a 1-1/2 in socket and using the nut on the cam pulley if you can rotate the engine with the socket and breaker bar you have a electrical problem,if you cannot rotate the engine you have a mechanical problem it is that simple.I bet a cold one if you hook 2 -8D batteries like the factory up to the starting system it will fire hot or cold    

[eagle19952]

i wonder...
like Clifford, not enough battery.
Because, cold is lower compression...it starts.
Hot everything is expanded..compression greater.
and battery is then "inadequate" 

[Fred Mc]

Ya, the battery thing has crossed my mind a few times. Changed from the 8d's to 3 950cca batteries a number of years ago and it working fine at first but then started having trouble. I just hate to spend $500 on 8ds and find it didn't make any difference. And once you buy then you can't take them back.LOL. And they don't fit in anything else I have. Maybe I can rent them. Ha.

Thanks

Fred

[dtcerrato]

I was going to change from two 8Ds to two group 31s and Luke at US Coach advised against that. That change was being considered by me when I was having starter problems. It ended up being the starter... I am now running two 8Ds (as we always have) with a different starter.

[eagle19952]

do like Clifford said...bar it over hot..
no turn/go ? 
it aint the starter/batts