1991 gl1500 se will not start

[Terry64]

just got this bike used 2 weeks ago... was 150 mi from home on a mini vacation in the mountains rode all day almost 300 mi bike was flawless parked at my hotel and .... here's the problem.

came out next morning and it wont start, spins over fine just no start.. brought it home on a trailer. here is what i have checked so far

All dash and warning lights come on as they should, kill switch is in run position and tested ok via cruise light, neutral light is on, 10.7 v at batt. and 10.5 on the black/wht wire when cranking, checked fuses and relays, side stand switch, angle sensor all are testing ok, Tach does not move at all when cranking engine

I am pretty savvy at chasing circuits however i cannot find a wiring diagram for this specific bike does anyone have a step by step to diagnose this type of no start.

i will take any and all inputs and suggestions, i will check it all again if necessary if it assists in trying to figure this out... i don't have the coin to take it to a shop and i am sure i can figure it out if i can get some direction. i found a post that gave some voltage check to perform on the ecm but it must be for a different year because i don't see the connectors they are referring to, my ecm is a black box with one huge connector on the end are there other locations to check ecm voltages? i don't want to buy an ecm until i can verify that that's what my problem is.

thanks in advance for any assistance that can be provided.

Terry

[MikeB]

You need voltage, fuel, and compression to make it run.

You checked the voltage and I doubt the compression went bad overnight.

What about fuel? Is the pump delivering fuel to the fuel filter?
Is the fuel filter clogged?
Is the fuel getting from the filter to the petcock?
Is it getting from the petcock to the carbs?

[Terry64]

hi thanks for the input, when i crank the engine a while i can smell gas i also gave it a shot of starting fluid to see if it would fire..no go i confirmed no spark when cranking put a spare plug in one of the wires to test.

[Bluewaterhooker0]

Assuming the meter you used is a quality device and accurate, that voltage sounds awfully low. Have you tried jumping in a car battery to assist the bike battery. And, I don't mean jumping as you would a car. Just attach the battery. The car IS NOT RUNNING. Or, even better, charge the battery to an acceptable voltage, or install a known good AGM bike battery.

[bluthundr31]

Cranking and no spark with battery at 10.7 volts sounds like time to charge/replace the battery. These beasts will "crank" over but not have enough to give spark to the plugs. CHARGE THE BATTERY and see if that resolves the issue.

[MikeB]

Cranking and no spark with battery at 10.7 volts sounds like time to charge/replace the battery. These beasts will "crank" over but not have enough to give spark to the plugs. CHARGE THE BATTERY and see if that resolves the issue.

Sounds plausible to me too. Sure way to find out is to do as Bluewaterhooker0 has suggested. Continue to monitor voltage as you crank it. Does the voltage drop below 11.0 vdc?

[Mh434]

I had exactly the same problem. Fine one day, cranked but refused to start the next, despite being on a smart charger during the night.

GL1500’s need a fully-charged battery with LOTS of juice to both crank & fire the ignition. I suspect that if you kept cranking it in very short spurts, at one point it would fire up as you released the start button.

This is a classic sign of a weak battery/weak alternator for these bikes. Their batteries are small & the draw on them is very high during starting.

I expect that if you were to jumper the bike with a spare, solid battery, it will start right up.

I’d recommend a replacement AGM-style battery & an aftermarket, updated alternator. That should fix it, for the foreseeable future. It certainly fixed my issues and, as a bonus, I now have a huge electrical budget to play with. I can add all the heated grips, clothing, lights, electrical farkles, etc. I like, and never worry about it.

[Terry64]

ok here is an update.

I tried the whole battery thing with two bike batteries and a car battery even at one time had two bike batteries in series and still no start.

decided to check the fuel pump again so if I jump the fuel pump to a battery it works gas flows... it is my understanding that this bike should run the fuel pump for 2 sec on key on and it does not, I put a probe on the power input to the pump and when I turn on the key it is my understanding from reading various post that this could be that the ECM has failed.

any way to validate that or do I grab one from eBay and give it a try

Thanks,

Terry

[bellboy40]

Your 1991 GL1500 does not run the fuel pump for a couple of seconds when the key is switched on. That was only the 88-89 models. You should have the pump running when cranking it and when it is running. See if you have voltage going to the pump when you are cranking it.

[bellboy40]

Here are some tests from the service manual to make. These should put you on the trail to fix the problem.

GL1500 ignition tests-1

GL1500 ignition tests-2

[Terry64]

Bellboy,

Thanks for the pages...

On your previous post you mentioned checking fuel pump power when cranking, i get 0 volts .2 on connection to volt meter goes to .6 when key is on stays at .6 when cranking

Thanks for your help..

Terry

[bellboy40]

I think you need to take the switch module off on the right handlebar with the kill switch on it. Then measure the voltage on the kill switch contacts with the ignition switch turned on. Check both side of the switch to make sure voltage is coming through it. Put your screwdriver on the screw terminals to make sure they are tight. I know in your 1st post you said the kill switch was on but lets check. If voltage is good there, go to the C54 connector (4 pin White) and check for voltage on the blk/wht wire. C54 is near the ECM on the right side behind the fairing inner cover.The voltage goes from there to the coils. Your fuel pump is powered by the ECM when it sees the engine turning over from cranking or running.
Also here is a simplified wiring diagram of the engine control circuit for the part we are interested in.

Engine control system

[Terry64]

thanks for the update, i will check this after work today and let you know what i find

thanks,
T

[Terry64]

checked kill switch 12V on contacts, made sure they are tight. checked blk/wht at c54 and also has 12v

all coils measure 425 ohms...

on the angle sensor i get 12v on white 0v on red/wht, is this correct?

thanks,

T

[Terry64]

coil measurement was wrong... had my ground probe on batt will check them again tonight

[bellboy40]

Those readings on the angle sensor look right but that is not your trouble anyway. If it will spin over with the starter all is good with it.
At the C54 connector where you measured the 12 volts at the blk/wht wire: Be sure the ignition switch is off and measure with an ohm meter between the blk/wht wire and the other three. You will be reading on the connector that goes toward the coils. That will check continuity through the primary windings of each coil. You should read a low resistance between each of them (approx 4 ohms).

[bellboy40]

I was looking back at your previous posts on the symptoms and noticed that you said the tach did not move when cranking. That blew by me when I first read it but that may be significant. Check the connector on the ECM. Take it loose and look at the pins for broken, bent or corroded pins. While you have it off check for battery voltage on the blk/wht wire going into the ECM. When you reconnect the plug, be sure it is connected firmly. Be sure the inner part (yellow) is connected properly. Often it is found to be loose or not plugged up properly.

[Terry64]

Coils all measure 2.9 ohms checked ecm connection all clean and plugged in correctly 12v at blk wht on ecm connector.

What do i check next

Thanks for the support on this...

[bellboy40]

All that sounds good. Did you make the tests for the pulse generators (PG)? That was on one of the pages I sent earlier. Here is the page with highlites where you need to test. If that is good, I am running out of ideas.

GL1500 PG tests at ECU

[Terry64]

Checked pulse gen. Wht/yel .9 wht/blu 430 ohms
This was checked at the ecm plug ..

Looks like i need a new one ...

Terry

[bellboy40]

That seems to be your problem. Usually the PGs in the 1500s are very reliable but stuff does happen. Hope you get it fixed soon.

[Terry64]

Thanks for all you help with this i will order the part and update this post when i am done

[MikeB]

Keep in mind that it may he a shorted wire between the pulse generator and the ECM, not necessarily a bad pulse generator.

[bellboy40]

Mike is right. Before ordering new PGs, make another test to be sure they are bad. There is a 4 pin White connector (C63) above the right cooling fan. That is where the PGs can be tested to further isolate where the problem is. This is the page from the manual.
If you will PM me your email, I have something for you.

GL1500 PG tests

[wingdings]

try this -

and then check the second starter solenoid - yes the 1500 wing has two !! - I had a problem like yours on my friends wing it turned out to be a loose plug connection on the second starter solenoid it would start and run for days then just die for no reason !! once the plug connection was fixed - it started first time !!- defo 100% check this out !! its a cheap fix too !! ..