4.0 died/no start

[joe_peters]

crank

For what its worth, on the Renix the Tach reads from the negative side of the ignition coil, per 1990 FSM.

 

[blue95xj]

That may be, but we are talking about a 99 which does not have a separate ignition module. Also he was looking at a scan tool and seeing rpm's. Not to mention when my crank sensor kicked the bucket on my 95 I had no tach reading at my gauges or on the DRB.

 

[joe_peters]

That may be, but we are talking about a 99 which does not have a separate ignition module. Also he was looking at a scan tool and seeing rpm's. Not to mention when my crank sensor kicked the bucket on my 95 I had no tach reading at my gauges or on the DRB.

Didn't see the "99" in the user name.

 

[gradon]

When my coil went a few weeks ago, I suppose it didn't fire a sequence or two and when it did fire, the unburnt gas in the exhaust ignited and made the biggest backfire I've experienced. No cel, and the coil ohmed out good b/t the two inputs(.6-1.2ohms) and a little low b/t primary and secondary: 10K, when it should've been 11-15K(the replacement bwd? ohmed out exactly the same as the defective one, so go figure).

 

[winterbeater]

You say you have fuel but no spark. Do you mean fuel rail pressure or the fuel is being injected into the cylinders? After cranking, do the plugs get damp? If injectors are still working, it seems that would rule out CKP (crank) and CMP (cam) sensors and lead you back towards the coil.

 

[99XJeeper]

I replaced the cam sensor and crank sensor with ones from a spare motor. Then i pulled out the old alarm system from the previous owner which was still wired into the ignition system. I grabbed this pic from another thread because i have 2 fuses that are not getting power and cant find them on Alldata or in any manuals.Does anyone know what the 2 fuses to the left side in the center are? the 15 amp with the 20 right above it.

 

[lawsoncl]

Both of those fuses are fed from the Auto Shutdown Relay. Its the larger relay on the upper right (C8). I think its normal to have that shutdown if the key has been on more than xx seconds without the engine started. Maybe try swapping it with the one just below it.

 

[lawsoncl]

The 20 amp fuse (#21) looks like fuel injector power. The 15 amp fuse (#24) looks like egr, o2 sensors, and possibly fuel pump.

 

[99XJeeper]

so when should i have power at those 2 fuses? ive been going through wiring diagrams trying to make sure the ASD relay circuit is fine. I have no power at fuse 21 or fuse 24.

 

[99XJeeper]

so when should i have power at those 2 fuses? ive been going through wiring diagrams trying to make sure the ASD relay circuit is fine. I have no power at fuse 21 or fuse 24.

edit: i have power at both fuses when cranking. is this normal?

 

[99XJeeper]

Im embarrassed to admit this but it was just a bad coil. Always double check the easy/common problems to save yourself the trouble.

 

[lawsoncl]

edit: i have power at both fuses when cranking. is this normal?

Yes. The computer controls the Auto Shutdown Relay (ASD). It turns the fuel off it it doesn't think the engine is running. For example key-on, but no sign of cranking for 10 seconds. It's a safety feature so an overturned vehicle doesn't keep pumping fuel.

Glad to see you tracked the problem down to the coil.