No spark...but what did I miss?

[Razorback1980]

Ok, I was helping another member here work on a no spark problem and I have missed something but I don't know what. These are the things I checked....

Pulled a plug and layed it on the intake and no spark at the plug.

With the key on..I have voltage at the coil on both terminals

With the key on, I have voltage to both sides of the injectors

Replaced the DME with a new one ...just because I had one

Unhooked the speed and reference sensors and both ohmed ok on two terminals but on the other two my meter stayed at 1...not sure why. terminals 8/27 and 25/26 both checked at 1050 ohms which is okay according to what little I know. When I would check 8/23 or 25/78 my meter would stay at 1.

Pulled a spark plug and put it in the coil wire going to distributor. Disconnected the negative terminal on the coil and connected another wire to the negative terminal and with the key on I touched the negative post of the battery with the wire connected to the negative side of the coil and the spark plug grounded. I was expecting a spark on the plug, but I got nothing.

I ohmed the coil between the negative post and the center and got 7200 ohms then I tested the ohms between the positive side of the coil and the negative side of the coil and got .6 ohms. Both of those readings are what I expected for a good coil. FYI...The coil is brand new. The distributor cap and rotor are also new...which means nothing I know.

Two things I thought of AFTER I left (I hate it when that happens) were maybe my coil wire was bad...never checked continuity (so I'm having him do that) and the other thing I never checked was to ohm between the body and the engine to see if I have good grounds.

What else should I have checked? Or does anyone else have ideas on why it is not getting a spark at the plugs.

[SoCal Driver]

Unless the dist rotor is lined up with the respective spark plug you will not get a spark. I've pulled a spark plug wire and the coil HV wire and used the coil directly.

As to the spark plug on the intake test; this is with cranking the engine. If there is no spark you need to make sure that the rotor is turning (broken timing belt) or that the sensors are plugged in correctly and/or adjusted correctly (1/32" or 0.8mm).

Could also be a bad coil to dist HV (high voltage) cable or the rotor could be burned through between the tip and the center or the center carbon-graphite pin on the dist cap could be bad.

Coil-dist cables tend to corrode under the rubber weather boots and get pulled apart when you change the filters or by the head light linkage if you don't repossition it after changing the filter.

[Razorback1980]

Thanks for the tips SoCal. I'll try the spark plug in the coil trick and see if that makes a difference.

The car did start occasionally and then it wouldn't. Now it just won't which is actually better because it makes it easier to test. Cap and rotor are new but I'll check those a little closer.

I didn't check the coil wire but I will on the next trip. Don't know why I didn't think of that when I was there. I did think about it after I left. The sensors were plugged in and I had to unplug them to do the ohm test on them. Not sure about the gap, but they haven't been moved or tampered with in any way during the last three years at least.

Thanks again, I'll check the coil wire and I'll put a spark plug wire on the coil and do the spark test again.

[earlr85944]

with everything connected, crank the engine, does the tach bounce?

[Razorback1980]

Yes, it did move but it only jumped to 300 rpms or so. Is that about right?

[earlr85944]

yes, connect a tach at the coil and do the same test.
You should get a tach bounce meaning all is good from the sensors to the dme to the wiring to the coil.
If you get a signal at the coil and still no spark look at the coil next then the coil wire.

[Razorback1980]

Thanks..coil was the first suspect, so it was replaced. Also did the coil ohm check and it checked per the clarks garage spec on both primary and secondary windings.

[earlr85944]

does that mean it was replaced and still no spark?
if so are you getting the "tach bounce" directly at the coil when a tach is connected directly to the coil?

[Razorback1980]

Hey Earlr85944....Haven't tried the tach directly at the coil yet, but I will. I didn't get in on the early diagnostics, but the car would sometimes start and other times not. I was told that when it wouldn't start, they could put a new coil on and it would start. When I got involved, the guy had a new coil in the box and I put it on and it still didn't spark. While I was there, I did the other testing in the first post to this thread. The thing I didn't think about until after I left was to check the coil wire which was really stupid on my part. I am thinking I'm going to go over on Wednesday night and have another look so I'm looking for suggestions on what i might have missed other than testing the coil wire.

I will put the tach on the coil directly on Wednesday when I am there. If there is anything else you can think of that I should have looked at while I was there, it would be great to know that. Thanks again for all your help.

[earlr85944]

if its starts when they replace the coil maybe its the wiring to the coil or after the coil that gets moved during the replacement. I went thought that with a sensor on a dodge 2.5 once, went through alot of "bad " sensors to discover it was the harness connector.
That is what the tach at the coil will help determine, you may get a tach bounce at the dash, doesnt mean its making it to the coil though, if you have the signal at the coil and 12v at the other side and the coil is good then check the hi volt wire to the dist, maybe an intermittent break?

Also recently had an intermittent on my 44 where it would start when it wanted to , ran for months fine, then drive it park it and BAM, no start ( of course at the worse tI'me) . After 2 flatbed trips it turned out to be the ref\speed sensor bracket was loose and I had a fluctuating gap... it also made the car run rich because I'm guessing it didn't read the pickup correctly and overcompensated with fuel.

[Razorback1980]

It could be the wire....shame on me for not testing that while i was there. I'll know more tomorrow night.

Thanks for the help.