GL1500 Carb Rebuilt, Won't Start

[viktorz]

Hi
.... I think I have a problem with the fuel supply on may GL1500 SE 1994. In addition to rebuilding the carburetor, I also:
- rebuild the fuel petcock
- replace the fuel filter, air filter
- checked the fuel pump minimum flow as described in the service manual (and is around 900ml / minute)
- determined that the Carburetor Control Unit Wiring Test is OK in all points like is in the service manual

I still can't start the engine unless I connect a jumper wire between the black/blue and black/white on the ECU and let the fuel pump run the fuel towards the carburetor for a few seconds. The fuel filter shows that it is not completely filled with fuel and the air is on top. Then I can start the engine, if I add gas, the fuel injection is clearly visible ...The engine runs until it consumes fuel ....I also checked to see if the fuel pump was heard when the key was turned on. I opened the fuel tank and listened but I can't hear the fuel pump running ....

Can anyone give me some advice on what could be wrong ... Thanks.

[viktorz]

Hi
... I did an additional test. I jumped wire between the black/blue and black/white on the ECU again and let the pump run for a few seconds to push the fuel to the carburetor. Then I disconnected the fuel hose from the fuel filter and put it into a plastic bottle. First I made key contact and looked at the bottle - nothing. I started the engine, which ran for almost 10 seconds, and monitored the bottle, into which not a drop of fuel flowed. It seems to me that the fuel pump does not get the signal to start. What is wrong? ECU? How do I check it? Fuel pump relay? How do I check it? Because the fuel pump obviously works if I connect it as I described above? Please help.

[DenverWinger]

Sounds like the fuel pump drive transistor inside the ECU has failed. If you have some electronics knowledge and soldering skills, the ECU is repairable.

See the below link for a "How to do it".
viewtopic.php?p=72687#p72687

[viktorz]

...Thanks for the quick reply. My son is an electrical engineer, I will give him the task to check the ECU .... I don't know when he will be able to do it, because we have this corona problem .... Maybe there is something else to check ....

[Rednaxs60]

Looked up your location. Vacationed in Slovenia a few years back, lovely country, scenery and people. Stayed in Ljubljana for a few days. Went para gliding north of the city. There is a tourist attraction, a series of caves to the west that we visited as well - lots of history there. When para gliding was high enough to see where the Germans came through the mountains. Good luck with your 1500.

[viktorz]

Everything is true, thanks for what you wrote....

[DenverWinger]

.... Maybe there is something else to check ....

Not really, since you jumpered power to the fuel pump at the ECU connector plug. The only remaining possibility is the contact for the fuel pump in the ECU connector is corroded or not making good connection.

[viktorz]

... OK, then first to check the transistor in the ECU ...

[viktorz]

Hi, I'm back. I found where the problem is .... The ECM and transistor are fine. I made a mistake once before when I tested the minimum flow capacity of the fuel pump and made a jumper wire between the black/blue (PIN3) and the black/white (PIN2) wire on the wire harness side. In all likelihood, I used too thick a wire and bent the bearing in the connector on PIN3. So when I connect the connector and the ECM, no contact occurs on PIN3. I discovered the problem but a new one was created immediately. The question is how to pull the wire with the connector out of PIN3 and fix it so that it will work when I finally connect the ECM.

Any ideas, Thanks.
Regards.

[4given]

Hi, I'm back. I found where the problem is .... The ECM and transistor are fine. I made a mistake once before when I tested the minimum flow capacity of the fuel pump and made a jumper wire between the black/blue (PIN3) and the black/white (PIN2) wire on the wire harness side. In all likelihood, I used too thick a wire and bent the bearing in the connector on PIN3. So when I connect the connector and the ECM, no contact occurs on PIN3. I discovered the problem but a new one was created immediately. The question is how to pull the wire with the connector out of PIN3 and fix it so that it will work when I finally connect the ECM.

Any ideas, Thanks.
Regards.

Read “Replacing Faulty Connectors” on this forum.

[DenverWinger]

Glad you found the problem....

[viktorz]

... I'll try to fix it. I'll let you know when it's done.

Thanks for all.

[viktorz]

So, I fix the connector and the fuel pump work.
I have read on various forums when a fuel pump is supposed to work. In my case (GL1500 SE, 1994) the fuel pump starts when I press the start button.

I started the engine, but I also noticed a few "explosions" in Mufflers. I know I still have to set the idle, the carburetor synchronization and the pilot screw adjustments (they were replaced by new ones).
What interests me is: Are these "explosions" in the muffler due to not adjusting the carburetor or is something else wrong (the spark plugs are new)?

Thanks for your answers and suggestions.

Viktor

[DenverWinger]

If you changed the spark plugs it is possible you have some spark plug wires crossed. That could cause backfires in the exhaust.

[viktorz]

If you changed the spark plugs it is possible you have some spark plug wires crossed. That could cause backfires in the exhaust.

...vauuu, what to say, you are the king. Thank you so much for all the advice and help. You were right! I crossed the spark plug wires between 2 and 4 (and if it weren’t written on the cables). Now contentedly purring like a big cat. I have solved this, it will be necessary to move on. Thanks again and I hope you will answer again if I have any questions.

... thank you all..

[DenverWinger]

I love it when a fix is simple!