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AC ACC40 Forklift Help - Weak Spark
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mynameisjonas View Drop Down
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Joined: 24 Jul 2025
Location: 90250
Points: 2 		Post Options Post Options   Thanks (0) Thanks(0)   Quote mynameisjonas Quote  Post ReplyReply Direct Link To This Post Topic: AC ACC40 Forklift Help - Weak Spark
    Posted: 24 Jul 2025 at 2:51pm
I have what I believe to be an AC ACC40 4 Cyl Propane forklift that is not running. It was running OK before we did some service and now we can't get it to fire again, and the spark is very weak. I replaced the voltage regulator, plugs, wires, cap, rotor, and coil. It turns over fine, but it will not fire. 

There has been some "modifications" to the electrical systems so I don't know where to go from here to diagnose the problem. The distributor is wired to the negative post on the coil and I believe that is correct due to "negative ground". I don't know what might be causing the weak spark with all of the new parts. 

Any help would be great! 


Battery is 12.6 volts
Power at the new coil is 10.2 volts 

Parts - mostly sourced from NAPA

Coil: Part #: BK S67080

Dist Cap: MPE RR181SB

Dist Rotor: MPE RR182SB

Wires: BK S65034
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Eric B View Drop Down
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Joined: 09 Feb 2012
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Points: 967 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Eric B Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jul 2025 at 12:27am
Hi Jonas, if you can include some details that would be helpful.  
Currently- WD,WC,3WF's,2 D14's B. Previously- I 600,TL745,200,FL9,FR12,H3,816 LBH. Earth has no sorrow that Heaven cannot heal!
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DonBC View Drop Down
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Points: 942 		Post Options Post Options   Thanks (0) Thanks(0)   Quote DonBC Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jul 2025 at 11:57am
Probably need a new coil. If the coil gets hot when running it would be a bad coil.
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jaybmiller View Drop Down
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Points: 24583 		Post Options Post Options   Thanks (0) Thanks(0)   Quote jaybmiller Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jul 2025 at 4:48pm
also , might need new 'condenser' ( capacitor). if it's the wrong value, you'll get a weak spark.
3 D-14s,A-C forklift, B-112
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DaveKamp View Drop Down
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Joined: 12 Apr 2010
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Points: 6052 		Post Options Post Options   Thanks (0) Thanks(0)   Quote DaveKamp Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jul 2025 at 10:13pm
Originally posted by mynameisjonas mynameisjonas wrote:

I have what I believe to be an AC ACC40 4 Cyl Propane forklift that is not running. It was running OK before we did some service and now we can't get it to fire again, and the spark is very weak. I replaced the voltage regulator, plugs, wires, cap, rotor, and coil. It turns over fine, but it will not fire. 

There has been some "modifications" to the electrical systems so I don't know where to go from here to diagnose the problem. The distributor is wired to the negative post on the coil and I believe that is correct due to "negative ground". I don't know what might be causing the weak spark with all of the new parts. 

Any help would be great! 


Battery is 12.6 volts
Power at the new coil is 10.2 volts 

Parts - mostly sourced from NAPA

Coil: Part #: BK S67080

Dist Cap: MPE RR181SB

Dist Rotor: MPE RR182SB

Wires: BK S65034
Ten Amendments, Ten Commandments, and one Golden Rule solve most every problem. Citrus hand-cleaner with Pumice does the rest.
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DaveKamp View Drop Down
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Joined: 12 Apr 2010
Location: LeClaire, Ia
Points: 6052 		Post Options Post Options   Thanks (0) Thanks(0)   Quote DaveKamp Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jul 2025 at 10:16pm
When I first looked at Jonas's post, all I saw was a blank box... turns out, the typeface color was same as background, which is why I quoted it above.

Jonas- I'm assuming you got the new parts installed properly, and that the point gap is set correctly... if so, there's one other part of the circuit that may actually be the 'whole' problem...

The keyswitch, and wiring.

You can test this by connecting a jumper wire from the battery directly to the coil's + post.  This bypasses all the ignition switch wiring... so the ignition system is 'on'.

Now crank the engine and see if you get spark.

If you do, suspect ANY part of the ignition switch and wiring.  Forklift ignition switches get LOTS of use, so they do wear out.
Ten Amendments, Ten Commandments, and one Golden Rule solve most every problem. Citrus hand-cleaner with Pumice does the rest.
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