Seeking advice, PCM GT-40

[DanE]

@Jody_Seal Just want to check with You if I´m on the right track with my troubleshooting.

1999 SN PCM GT-40, suddenly started to lose one cyl, intermittently.Thought I had narrowed it down to injector #1 as the engine showed no response to pulling the connector on and off, suddenly it started to work only to have the same symptom showing up on #4 and then that injector started to work by itself.Measured resistance from the ECM to the injectors-all good.Measured resistance at the injectors-all good, measured fuel pressure-great.Then measured voltage between posts on connectors on three different injectors while engine running-really low.Measured it with a FLUKE voltmeter with rec. function to record min and max voltage and only got around 0.6 volts.Measured voltage from connector directly to ground-14 volts.Checked these measurements on both banks.Figured I had a bad ground connection from ECM to ground- all ground connections were good.So I figure I am looking at a new ECM?Are there still ECMs availible to these engines?

Thanks in advance.

[lb]

I ran into this last year on a 2002 with a lot of hours. intermittent skips I to went through trying to make it a fuel issue, finally put a jumper wire in place of the safety switch and it ran great. replaced the switch all is good.

(the safety switch shuts down the fuel pump on the motor when the lanyard is pulled if there is a bad connection or a faulty switch it cuts the fuel pump out and back on quickly reducing fuel pressure, but when sitting still at an idol it does not show as a problem.)

Good luck

 

[DanE]

Thanks @lb.

I have already installed that jumper wire and besides, I monitored fuel pressure with symptome present- fuel pressure is Good, wich it would not have been if the lanyard jumper was bad.

[gregy]

@danE what about sensors. Somethings got to tell it when to fire the Injector. Distributor maybe. You might get on the Nautique forum.

[DanE]

@gregy, the problem seems to lie in low voltage yo the injectors caused by the ECM as far as I can Tell on the ground side.Have ordered one with my local PCM dealer.Will let you know how it went.

[Jody_Seal]

@DanE, How many hours on this engine? there are two relay's on the ECM bracket, have you checked them for terminal degradation? did you swap the relay's? one Relay controls power to the fuel pumps the other to the ECM, The relay with the Green wire's is the fuel.

ECMs are starting to get few. PCM still does offer them but they are pull off units and they are getting a premium for what they have. you might not get the 300m ECM and if the ECM needs replaced no guarantees that it will be new!

[DanE]

@Jody_Seal Close to 2000 hrs, runs like New (normally).

Yes I've checked the relays, like I Said in my first post I have 14 volts at the injectors if I measure from the connector post to ground.The voltage is low(Only 0.6 volts) when I measure between both posts on the connectors, therefore I figured it to be a problem witth the ground. Since both wiring between injectors and ECM and ECM and ground were Good i thought it could only be the ECMs fault.

Now, you make it sound like i need to get me an ECM regardless..

[Jody_Seal]

I have one I can send you to test with. PM me your address and I will get it out. Sorry though it is the only one I have and I need it back. I can call PCM and see what the availability of one is if indeed you need another.

[DanE]

@Jody_Seal Have one on order with my local PCM dealer.Tank you for the offer, might take you up on that if PCM doesn't come through.

[vonzipper]

A little food for thought, I just went through the same thing with my 2000 SN 196 PCM GT40, checked my fuel pressure and it was good at idle, the gauge vibrated a little at WOT,I could swear I had a misfire somewhere, checked everything, found my low pressure fuel pump putting out the correct pressure just not the correct volume, swapped the LP fuel pump and happy days are here again.