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LH2.4 crank no start

D.E

tvåförti
Joined
Sep 15, 2010
Location
Mora, Sweden
So my 240 has been sitting and suddenly died when I was moving it. Charged up the battery but it just cranks. The CPS sensor had some chafed wiring so I replaced that with an old OEM one but that didn’t do anything. I tried another no-name one from the parts store but no difference. I also tried swapping the powerstage with a known good one.

Cranks but no fire
No fuel smell
Fuel gauge shows top of reserve
Main lead to dist sparks when I turn key
No spark at plug while cranking
Plugs are dry
Rev counter does not move
Fuel pump is buzzing
Didn’t skip timing
Ran perfectly then didn’t.

Any clues? Could all three CPS’ be bad?
Is there anything else that could cause the plugs not to spark and the injectors not to fire? Random sudden ECU death?
 
So the car is built in 1988 but it is a 1989 model year.

Have you checked the fuel injection fuse on the left inner fender next to the battery? If it is corroded or blown, you will not have working injectors
 
So the car is built in 1988 but it is a 1989 model year.

Have you checked the fuel injection fuse on the left inner fender next to the battery? If it is corroded or blown, you will not have working injectors
Yes.

I pulled the fuse and the fuel pump quit buzzing so I assume it is not the culprit.
 
I inspected both the flywheel and dizzy shaft and both are spinning as they should while cranking.

I also peeled back the boot on the CPS connector and inspected the pins and wiring and it all looked good.
 
No spark!?

Got injector pulse? Test lamp between negative injector wire and ground. Blink?

Test lamp between coil negative and ground. Blink?
 
No spark and no fuel can be the fuel pump relay. It is a two sided relay and if it's dead then the computers on the system side of the relay don't turn on. If they don't turn on you don't get spark or fuel.
 
If you have ignition current going into the distributor and nothing on the spark plug side either the cap or rotor is bad.
 
No spark and no fuel can be the fuel pump relay. It is a two sided relay and if it's dead then the computers on the system side of the relay don't turn on. If they don't turn on you don't get spark or fuel.
Tried a different relay, no difference.
 
If you have ignition current going into the distributor and nothing on the spark plug side either the cap or rotor is bad.
There’s a quick spark from the lead going from the coil to the cap right as I turn the key, then nothing. What does this mean? Shouldn’t there be a constant current to the cap with the ignition on?
 
No spark!?

Got injector pulse? Test lamp between negative injector wire and ground. Blink?

Test lamp between coil negative and ground. Blink?
I have 12v at the injectors and 12v at the positive coil terminal.

I measured all three CPS and they all showed ~170Ohm between pin 1 and 2 which should be good.
 
There’s a quick spark from the lead going from the coil to the cap right as I turn the key, then nothing. What does this mean? Shouldn’t there be a constant current to the cap with the ignition on?
Ok that quick spark is normal. It's the powerup of the system with key on. However, if the spark is not generated then you don't get fuel. I would get out a test light and make sure that the fuel pump and system side of the relay turns on.

If the relay isn't turning on that could be the ignition switch not powering up the system side of the relay. Once the system side of the relay powers up. Then the fuel ecu looks for the engine rpm signal to know it makes spark and it's cranking. If that works then your ecu turns on the fuel pump.
 
In addition no spark conditions I've encountered were either the rpm sensor or the EZK itself. Barring any wiring issues those are the only options when there is no spark and no trigger detected to make spark. Under the LH2.4 diagnostics you can run a test on the rpm sensor if I recall correctly.
 
Try turning the ignition switch/key to the run position and then trigger the starter using a remote starter switch and see if it starts. You may have a bad contact in the ignition switch.
 
Alright so the car is running again. Thanks for all the suggestions! I didn’t read them all in time but it may help someone else.

It ended up being the ignition computer that failed. Unfortunately I can’t be helpful in how to diagnose this since I just started swapping parts with known good ones until the car started.

A reminder that it’s good to keep at least one spare of every electronic part of an old car if you need to depend on it. :)
 
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