98 G3500 with no spark

I came back to visit family and found myself trying to help fix this thing. Here is what I know.

My brother in law owns the van and when purchased it was smoking badly and barely moved. (vehicle has just over 500K on it) Motor and trans have been rebuilt. I was told there was no spark from coil. Also told coil was checked and checked out good, but replaced anyway. New plugs and wires.

I pulled #1 plug and verified TDC/distributor setting. Checked for spark coming from coil - nothing. pulled connector from coil, turned on key have power on one wire(purple or brown - cant remember) I can hear the fuel pump running and can smell fuel while cranking. I have a couple of more days here before heading south again. My brother in law really would like to get this going as it has been sitting for over 1 year now. The mechanic who helped do this is a family member and has became stumped and just forgot about it.

Any help would be greatly appreciated.

Chad

I would take the module to Advanced or Auto Zone and get it checked they will do this free. Check the rotor button and distributor cap. Unplug the pickup use a analog DVOM and put one lead in each connection the gage should sweep as the engine is cranked.

I would take the module to Advanced or Auto Zone and get it checked they will do this free. Check the rotor button and distributor cap. Unplug the pickup use a analog DVOM and put one lead in each connection the gage should sweep as the engine is cranked.


The module checked out ok. Button in top of cap has small amount of wear on it, does not move. Cap looks to be in good shape no cracks noticed, small amount of oxidation on tabs. rotor looks to be ok.

I put a digital meter(no access to an analog meter) to the wires from the pickup coil and from the outside 2 wires got 11.9 volts with key on and about a 9.4 - 9.6 while cranking. while touching center to right I got about 11.8 with key on and 8.5 - 8.6 while cranking. Is this bad? Where is the voltage feed coming from?

Chad

If the module is good then I would check the crankshaft position sensor. If it is bad then the ignition module won't send any ground pulses to the negative terminal on your coil because it's not getting the signal from the sensor.

If the module is good then I would check the crankshaft position sensor. If it is bad then the ignition module won't send any ground pulses to the negative terminal on your coil because it's not getting the signal from the sensor.


I checked the ohms thru the pickup coil and got 1682. I have read where it should be between 500-1500, with this being high is it bad? will do some looking into the crank position sensor.

chad

found out there is no way to test the crank position sensor. When I look up a cam position sensor(Parts house website) it shows the pick up coil. Is there a cam sensor on this? I believe the motor is a 5.7L.

Without being able to test the crank sensor do I bite the bullet and spen $60, or send it to a shop and have a diagnostic done? Or is there something else to look at first?

Thanks, Chad

found out there is no way to test the crank position sensor. When I look up a cam position sensor(Parts house website) it shows the pick up coil. Is there a cam sensor on this? I believe the motor is a 5.7L.

Without being able to test the crank sensor do I bite the bullet and spen $60, or send it to a shop and have a diagnostic done? Or is there something else to look at first?

Thanks, Chad


Did it ever set any codes?

Crank shaft sensor needs tested with a lab scope or with good engine capable scanner watching rpm signal.

I am not much on throwing parts at it but it will cost as much to have it tested as just putting on on it.

If coil and module is good go for it.
Good luck and.
Let us know how it goes.

The ground wire for the coil should be pulsed for the coil to fire. Try a logic probe on the ground wire it should blink as the engine is cranked. The coil has 12 volts and fires when grounded as the distributor turns into the proper position.

Did it ever set any codes?

Crank shaft sensor needs tested with a lab scope or with good engine capable scanner watching rpm signal.

I am not much on throwing parts at it but it will cost as much to have it tested as just putting on on it.

If coil and module is good go for it.
Good luck and.
Let us know how it goes.

I asked at the parts store about renting an OBDII and checking for codes, but was told that if it does not run, it will not set a code. So no I have not checked for codes.

The ground wire for the coil should be pulsed for the coil to fire. Try a logic probe on the ground wire it should blink as the engine is cranked. The coil has 12 volts and fires when grounded as the distributor turns into the proper position.


I will try to do this before the crank sensor. What is next if I dont get a pulse from it?

I asked at the parts store about renting an OBDII and checking for codes, but was told that if it does not run, it will not set a code. So no I have not checked for codes.




I will try to do this before the crank sensor. What is next if I dont get a pulse from it?

Normally if you do not get the ground pulses to the negative side of your coil when trying to crank the next step would be to check your ignition module which you say is already tested good, and from there I would suspect the crank sensor.

Most shops charge $85.00 for an Hours diagnostic. If your wires look good around the distributor replace the pickup if you have no pulse.
On these I use a Thexton plug adapter for a place to hook up my scope. If you use a bed of nails or straight pin coat the hole with silicon. The wire will be hard to get a place to get to a tester attached.

I appeciate the help folks. I will be looking into this after lunch and will post some sort of results.

Thanks

I agree with Rhandwor, I was thinking about a different system when I was giving advice, sry for the bad info about where the ignition module gets the signal from on your vehicle. The problem like he said is more than likely your pickup coil.

well no luck today. I am out of time. My brother in law is going to let me know what it is when he gets things looked at. Will post here at that time.

What did you find was the cause?

I did not have enough time to figure it out. My brother in law is to get it figured out and let me know. I will post then. Hopefully he will get it going soon.

I did notice that the screws for the rotor where quite long and digging into the pick up coil. The pick up coil was ohming out at the same as a new coil in the store. Also it looked as tho the rotor tab was short. If the rotor tab is too short will it cause things not to pick up and fire?

I would get proper length screws for the rotor. They may have grounded the pickup when touching. Measure the rotor length with a new rotor. Are you sure something isn't broken. Ohm from the center post hole to the tip I found bad ones before.
If the screws were cutting the pickup on my vehicle I would change it as it probably has some damage.

I told him when I left to get a new rotor and pickup coil. As soon as I hear from him I will be sure to post the results.

Thanks.

Long time no post. Truck is still not running but I have come across a few things that I believe may be the issue. I see that someone has used screws that are too long to hold down the rotor and that they are digging into the pick up coil to the inside of where the distributor passes through. I also see that the rotor tab seems too short to me(burnt). I believe the issue lies in this area. We did replace the crank sensor with no luck.

I am going to try changing out the cap and rotor first, then the pick up coil. Although I am concerned that maybe the PU Coil is misfiring and grounding out.

Remember to purchase proper length screws or the problem will reoccur.

ok here we go again. I have replaced the camshaft position sensor and still no luck. I have a wiring diagram and followed it to the make sure the fuses it showed in it were good and found the fuse marked ENG1 was blown. I replaced the fuse, still no start. I did not check for spark after this. Am I down to the ECM?

Also, I found out that the Ignition Control Module has NOT been replaced as previously mentioned. I do understand this is not a part that can be tested.

What is my next step?

All help is much appreciated. Thanks

WE GOT IT FIGURED OUT!!!!!:runaround::runaround::runaround:

My brother in law and I came across a van sitting. Inquired about the side doors(no glass) and hood and got them for $40. He also threw in the ecm for us when we told him of our issues. The ecm was for a 6cyl, but he said it would at least try to start or run on 6 of the 8. The van did try to start, so we have ordered a replacement and should have it running by the weekend.

I appreciate all the help and ideas in getting this going.

Thanks,
Chad