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99 600 EFI ECU test????

M
Jun 19, 2008
59
6
8
Is there anyway to test if a ECU is bad.

A little background:
99 Powder Special 600 EFI lost spark last year. Fixed stator over summer. Put on maybe 400 miles and thought I was fouling a plug. Shut off replaced both plugs went to restart and no spark. Got it home checked stator found primary charge coil to have a very high resistance. Stator Corp sent me the new coil and installed my self. Put it back together and still no spark. Rechecked all resistances on everything I had a value for, and everything looks good.

I am now suspecting a bad ECU but am not sure of a way to test it. I am open to any suggestions.

Thanks for any help,
Tim
 
Last edited:

vdo1948

Well-known member
Lifetime Membership
Nov 26, 2007
794
119
43
Eastern South Dakota
Haven't had the no spark prob, but some years ago was fighting my 99 PS. Mechanic ran out of things to try. Suggested I buy a used ECU and try it. He said there was no real way to test them. Turned out to be the TSS - my first and maybe still best lesson learned from Snowest forums. Still have the ecu if you want to buy or borrow. Don't remember which symbol. Where you located in MN?
 
B
Dec 5, 2007
316
53
28
It could still be the stator. Check your specs again. Here they are:

Brown/Green 450 ohms
Brown/Black 495 ohms
Green/Black 45 ohms

Here is a spark diagnosis process to go through with your sled:



Open Ignition: Newer style ignition including the 1998 and newer ZR’s and ZL’s 1998-2002 ZRT 600,800 and 1000
A "normally open" ignition system. With this system a live wire goes from the ignition system to all of the switches. The switches are normally open, or not making connection, until in the "OFF" position. When in the "OFF" position the switch will ground the ignition wire to the chassis effectively "grounding out" the ignition system killing the spark. If a connecter becomes disconnected or if a wire gets cut then the switch will no longer turn off the engine. With the "normally closed" system if a connector comes loose or a wire gets cut the spark will stop until the wiring is repaired completing the circuit again.

Diagnosing no spark, weak spark or intermittent spark issues

The first thing you want to do is separate if it an issue in the switches/handlebars or lights or if the issue is in the primary ignition components like the stator, cdi, coils, trigger coil or possibly plugs or plug wires or plug caps.

1. The first thing you want to do is to take the spark plugs out of the cylinder heads, put the spark plugs in the spark plug boots and lay them on the cylinder head so they are grounded. A good place is on a cylinder head bolt away from the cylinder spark plug hole. If you pull the sled over and the spark plug is over the spark plug hole and it sparks it will ignite so make sure the plugs are not near the spark plug holes.
2. Pull the recoil rope and check the spark at the plug. Is there Spark? Is there spark at each spark plug? IS the spark blue (indicating a strong spark) or is it yellow (indicating a “weak” spark).
3. The next step is pretty much the same if you had no spark or a weak spark. On the “open” ignition you can simply unplug the 4-prong connector containing the 2 yellow wires. On some EFI sleds you have 3 yellow wires and one non yellow (ground) wire. The extra yellow wire is used for powering your fuel pump. The other 2 yellow wires in the 4-prong connector sends the power to the lights, hand warmers and tachometer. When you unplug this 4-prong connector you are bypassing all of your switches (Throttle Safety Switch, Kill tether ect..) and all of your lights, hand warmers ect..in your handlebars. Pull the recoil over and see if you have spark or if the spark is now blue. Carbureted models can be started and run with this 4-prong connector unplugged but you won’t have lights ect..as mentioned before. If you have an EFI, you can only check for spark and it will not start or run with it unplugged. You need it plugged in to power your fuel pump.
4. If you had no spark and by unplugging the 4-prong connector you now have spark, that tells you that you have something shorted out in your hand controls, switches like the tether, throttle safety switch or kill switch. If you had weak spark and now have blue spark it also tells you that you have a short or a problem with one of your switches. The most likely culprit is the TSS or kill switch, There is a 3 prong connector in your handlebars that if you unplug it will bypass your kill and TSS switch and you will only be bale to start and turn off your sled with the key. The 3 prong connector is usually not by the handlebars next to where you put your hands but rather just a little bit down the steering shaft about at the point where the console containing the key switch is located. If you’re not sure which connector it is, just follow the one group of wires out of the right handlebar area where the TSS and Kill switch are located down to where the plug is located. There are 3 other plugs by the handlebar on the right side by the thumb throttle, but they contain yellow wires and are for your hand warmers and thumb warmer and do not have anything to do with the TSS or the Kill switch.
5. If after unplugging the 4-plug switch you still do not have spark or the spark is weak looking this tells you that the problem is in the major ignition components like the stator, coils, cdi spark plugs, spark plug wires or trigger coil.
6. The first thing to check are the connections from the stator to the cdi. Make sure all connections are free of moisture, are tight and use dielectric grease on it. Check the ground. You should have a ground wire coming from your stator and your CDI/ECU box. Make sure the ground is clean, tight and that the ground wires are not broken. Sometimes the ground wire is pinched and broken inside the eyelet connection and is making only intermittent if any connection. Some older model Arctic Cats have the ground up closer to the handle bars on what some would consider the “firewall: of the sled and they are notorious for rusting/corroding out badly.
7. If all of the connections are solid and the ground looks good then you have to start electrically checking components. Most of the twin trigger coils are supposed to ohm out at 90 or so ohms. Triples are usually 175 ohms. View my “testing a pulser/trigger coil” video to see how to test it. It is very easy and quick to test. The frustrating part about the trigger coil is that it can test good, but still be bad.
8. Next you want to test the stator itself. View my “How to test a stator” video to see how to do it. Here is a list of Arctic Cat specs. I am continually adding to it so the list will grow over time so keep checking back:
9. If you have no spark and your trigger tests ok and your stator tests ok then we’re looking at a possible bad CDI box There is no real good way to test the CDI other than swapping the box out with a known good CDI box.
10. If you have no spark and your trigger tests ok and your stator tests ok then we may be looking at a secondary coil issue. The coils can have a couple of issues with them. The first thing you want to do is make sure the spark plug caps are on tight. They just screw on and off the spark plug wire. Many times the best thing to do as long as your wires are long enough is to unscrew the spark plug caps, trim a ½ inch off the end of the wire and then screw the spark plug cap back on. Also, you can unscrew the wire from the coil itself and do the same thing. Trim off about a ½ inch and screw it back on the coil. I had 2 sets of coils go “bad” on my sled and come to find out it was just the spark plug wires were a bit warn at their ends and after I trimmed them and screwed them back together they ran perfect. This condition usually causes a miss or it sputters at higher rpms. Be warned though that I did have one wire that would not unscrew from a coil no matter how hard I tried to turn it and I ended up just tearing the spark plug wire. Also, always check the spark plug gap and set it to the correct spec for that plug. I have seen plugs with the gap too small onthem maing the motor run poorly.
As far as putting the coil wires back on here is a general rule of thumb for Cats:
Most sleds fire all the plugs at the same time, multiple times per revolution. A twin will fire both wires twice each revolution, a triple three times( once per 120 degrees because every 120 degrees one of the pistons is at TDC). One of the pulses fires the plug to ignite the fuel/air mix, the other times the pulses are "lost" as the plug fires with the piston not ready for the fuel to burn. That prevents having to have a complex distributor of some kind to route the electricity to the cylinder that needs it. On those types of ignitions, firing order (which spark plug wire goes on which spark plug) is not important.

11. Specificly on Battery EFI sleds here is another thing to check. This was found on a 1996 EXT EFI: it was the relay on the back of the ecu. There are 2 of them back there 1 for the spark and 1 for the fuel pump.
12. Also, bad reeds on a sled will cause it to back fire and run poorly acting like it is an electrical issue.
13. Sled won’t shut off condition: I have seen a few things cause this. First off it is usually a bad ground/broken ground wire. Sometimes it is moisture in the connector. I disconnected my TSS/Kill switch the day my kill switch got moisture in it and my sled wouldn’t shut off. You could have a cdi with an internal short. A bad stator has caused a machine to not shut off.
14. Other issues/symptoms that I have seen/read related to a no spark/Weak Spark/Wet Plugs issue:
A. A guy bought a used sled with the wrong flywheel on it.
B. Frayed wires somewhere in the wiring harness or under the seat were causing a short
C. Guy said sled was only running on one cylinder. He could remove one spark plug wire and it didn’t effect the way the sled ran. His low side coil on his stator read 360 ohms and it should have measured 450 ohms. His low side coil was dying.
D. It kept fowling plugs left and right. What I found out was that the guy before me ran ethanol, and never told me. This was on an EFI sled.
E. Hood harness was routed between rewind/stator housing and frame and had 4 wires smashed. Repaired wires and cant find any other faults with sled.
F. Got it running again tapped the ECU and died. Pulled the ECU cover off and found some corrosion
G. I noticed some wires running to the carbs that were rubbing against the jack shaft (Shaft going from secondary clutch to the top sprocket in the chain case). After re wrapping/re routing the wires and I have NEVER seen it run better than it did tonight.
H. Bolt for the recoil cup broke off and hit the trigger coil, bent the bracket slightly and gave it too much airgap
 
M
Jun 19, 2008
59
6
8
Thanks for the replies guys.

vdo1948- I already have the TSS disconnected but I may be interested in that ECU of yours. I have a friend with the same sled so I plan to pull my computer and plug it into his to see if its faulty or not. I will let you know.

Blaine- Brown to Green I have 438 ohms
Black to Green I have 38 ohms
I haven't checked Black to Brown but I will. I will also check for the relays. I hooked my multimeter into the fuel pump circuit and saw a voltage being sent to the pump when I pulled the rope but nothing to the coil. So if I have the relays that would be a possibility. Are they typically located on the back side of the ECU so I have to remove the ECU to see them?

Thanks again guys.
 
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