2001 Cat Z370 Problem - Help!!!

M

mride460

New member
Have a 2001 Cat Z370 and it looses a cylinder at idle.
The compression numbers are within a pound on both sides.
The carb and jets are clean.
I changed the caps on the plug wires and there is great spark on both sides at idle.
I just dont get it, if you give it gas it comes back and runs great but back at a normal idle rpm it falls back off.
Any ideas out there????
 
J

jimfsr

New member
check your air screw settings, should be about 1 1/2 turns out from lightly seated. (starting point) also be absolutely sure the pilot jets (small one) are perfectly clean, you should be able to see light through them. Last idea, make sure the enricheners (choke) plungers are sliding freeely. they can corrode and hang up in the open position, flooding the cyl.at idle.

what are the commpression #s? should not be less than 100. It might run, but not great.

it really sound most like a plugged up pilot jet, picks up fuel when on the high speed jet.

If the enricheners are working ok, try pulling the enrichener cable on the dead cyl up slightly to see if it picks up rpm.
 
M

mride460

New member
I have the air screw at 1-1/4 turns. The compression is at 104-105. There is only one carb and the pilot is clean. I've had the carb apart 3 times this week to make sure. I'll check on the choke but wouldnt it affect both cylinders if it wasnt working right?
 
J

jimfsr

New member
Ok. One carb, problem is not fuel related, or it would affect both cyl. Compression is close to needing a re-build, but that could also depend on you guage, make sure you pull it over till the needle stops moving.
Another idea... is it the cyl. that the fuel pump pulse line attatches to? If the pump diaphram has a pinhole it will feed fuel to that cyl. unregulated. The line from the pump to the crankcase should be dry inside, no fuel at all.

That motor uses a duplex coil right? (both wires from one coil pack) or does it have 2 seperate coils?
Use an automotive timing light to check if both plugs are firing at idle. Check for a steady pulse of the light, should not be intermittent.
Did you clip off 1/4" of the plug wire before you put on the new caps to get fresh wire?
 
M

mride460

New member
I will check the pulse line tomorrow. Yes it only has one coil and both plugs are firing correctly. Checked with timing light like u said. Yes I cut of about 3/8" of plug wire to install new caps. I will have to recheck compression tomorrow also just to make sure I did it right.
Thanks for the info. I will update tomorrow evening.
Mike
 
M

mride460

New member
Ok guys. The pulse line is dry. I bought a new comp. tester, a good one that screws tight into the cylinder. Re-checked the compression, pulling until the needle stopped and both sides were dead on 126lbs. Did it 3 times to make sure. Pulled the carb back off and checked the jets out. Clean as a whistle.

The machine only has one coil. Is it possible that one side of the coil is not working properly at idle??
 
S

sabercat

Member
Adjust your slides and choke cables. Then start from there with mixture / rpm settings

On twin carburetor models if a carbureator choke cable is adjusted too tight, the engine will only operate on 1 cylinder at idle.

Should only be 1/8 inch play between base and lever when pulling up on choke lever in the off position.
 
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M

mride460

New member
sabercat said:
Adjust your slides and choke cables. Then start from there with mixture / rpm settings

On twin carburetor models if a carbureator choke cable is adjusted too tight, the engine will only operate on 1 cylinder at idle.

Should only be 1/8 inch play between base and lever when pulling up on choke lever in the off position.
Click to expand...

It is a single carb set up and the choke is adjusted properly.
I'm pretty sure its not a fuel issue. It has a single coil that runs both plugs. Could one side of the coil have a problem?
 
6mile

6mile

Member
mride460 said:
It is a single carb set up and the choke is adjusted properly.
I'm pretty sure its not a fuel issue. It has a single coil that runs both plugs. Could one side of the coil have a problem?
Click to expand...

Check the resistance from one plug wire to the white wire the check the other. if the resistance in not with in 5% borrow a coil from a good working sled and try.
 
M

mride460

New member
Ok. I'm still having problems. Loosing RH cylinder at idle.

Compression is 126 on both sides.
New coil.
Cleaned carb and jets.
Bypassed the throttle saflty switch.
New gas with some sea-foam in it.
Fuel pump is working and the pulse line is dry.

I am racking my brain to think of something I may be missing here that could be causing this.

Anyone have any more ideas that might help??????
 
E

ezra

Well-known member
dumb ? did you try running after switching plug wires around is pto not working if you do that or still mag side? I assume U did new plugs right? I 1 time had a bad plug wire that was arcing off head could not see until running in gar with lights off and headlight unplugged
 
J

jimfsr

New member
if the constant is the right cyl. I would suspect a crank seal, but normally a vac. leak like that would make it idle higher or would gain idle speed the longer it idles. But, if you feel like pulling the flywheel and stator plate, you should be able to see some evidence of a bad seal. either burned rubber dust, blow by evidence, or even the seal blown out of place. I have seen it before, it can do some wierd things.
 
M

mride460

New member
Thanks for all the help guys. Believe it or not I messed around with the air screw on the carb a bit more and then checked the gap on the new spark plugs. The gap was a little wide on the plugs. Runs real good now!!
Pretty dumb not to check something so minor!!

Thanks again...
 
S

skutr

New member
Don't feel bad - I did the same thing on my riding mower this summer. It would start, mow for a little while and die. I went through the entire electrical system only to discover that the safety switch on the seat was bad. One jumper wire and fixed.
 
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