Crank, no spark, no fuel

[Timothy McManus]

I have an early 1993 RT/10, was running great until I went out to the car one day and it just cranks, but never fires over. I checked all of the fuses in the passenger footwell, they were all good. No smell of gas out of the exhaust after cranking. I put a spark tester inline with a few of the spark plugs and I’m not getting any spark while cranking. I can hear the fuel pump running for 2 seconds when I turn the key to run so I am assuming there is good fuel pressure. I have a fuel pressure gauge, but don’t see a shrader valve anywhere to measure it. When I check the engine codes I get:

12 Direct battery input to PCM was disconnected within the last 50 key-on cycles (normal)

33 A/C clutch relay circuit

55 End of error messages

Code 33 has always been there, but idk if it could have anything to do with this new issue.


My thoughts are a crankshaft position sensor, camshaft position sensor or ignition module or something else that I’m unaware of. Does anyone know a way to narrow down the problem?

 

[Viper Specialty]

Crank engine. Listen for fuel pump run-on for a second after engine stops rotating. If you are getting FP activation, unlikely to be crank sensor issue, more likely Cam sensor. Otherwise, no FP activation when cranking often = bad crank position sensor.

 

[Timothy McManus]

I put my hand on the fuel pump relay and could feel it kick on and prime for 2 seconds when the key was turned to Run. Cranked the engine over for about 5 seconds and felt the fuel pump relay turn on for maybe ½ a second. Cranked the engine a second time and did not feel the fuel pump relay turn on at all. I have a new crankshaft position sensor on the way and will update once I get it switched out.

Thanks Viper Specialty for the helpful insight

 

[Goggles Pizano]

Did you look at the rpm gauge as you were cranking?

 

[Timothy McManus]

The tachometer didn’t move at all while cranking, but I did get some oil pressure after a few seconds.

 

[Goggles Pizano]

Crank sensor.

 

[Timothy McManus]

Just replaced the crankshaft position sensor, still no spark, no fuel, and no rpm showing on the tach. Any other ideas that I can try?

 

[Timothy McManus]

I checked all the fuses, and checked power and ground to the ignition module and ECU. Everything looked good there Are there any hidden fusible links that might be blown?

 

[Viper Specialty]

If you are 100% sure you are getting power/ground at PCM and IGN, have a good crank position sensor, good crank position sensor wiring, fuel pump activation at key-on... the last hail-mary is a Cam Position sensor [unless you are capable of probing the sensor output with a DVOM and manually rotating the engine waiting for the sensor output to change in order to verify functionality].

Beyond that, your PCM becomes suspect in a hurry, it may be dropping out right after activation due to internal shorting. We are the supplier for those, but you need to check sensor inputs first.

Unfortunately your hands are largely tied without access to a DRB-3.

WARNING: If your PCM is dropping out shortly after key-on, you are absolutely riding the edge of a full-on PCM meltdown. I strongly suggest leaving the PCM disconnected when you are not actively working on the car until the problem can be verified. PCM meltdown can occur even without the key in position, as they are powered all the time. Cost difference to replace a PCM without a core vs with is huge. Dont risk damage pointlessly while figuring this out.

 

[Steve-Indy]

Have you tried swapping the ASD relay with the starter relay...since you know that the starter relay works ?

 

[Viper Specialty]

Have you tried swapping the ASD relay with the starter relay...since you know that the starter relay works ?

Normally I would agree, but if his fuel pump relay is deactivating mid-crank, something else is going on.

 

[Steve-Indy]

Good point, Dan.

The Schrader valve port for reading fuel pressure on an early Gen I is at the very rear of the driver side intake manifold... noting that it faces the driver. You might need to remove the windshield cowling to get to the port. It might be helpful to put the gauge on it before and during cranking engine to be sure that you understand just what the fuel pump is doing.

 

[Timothy McManus]

If you are 100% sure you are getting power/ground at PCM and IGN, have a good crank position sensor, good crank position sensor wiring, fuel pump activation at key-on... the last hail-mary is a Cam Position sensor [unless you are capable of probing the sensor output with a DVOM and manually rotating the engine waiting for the sensor output to change in order to verify functionality].

Beyond that, your PCM becomes suspect in a hurry, it may be dropping out right after activation due to internal shorting. We are the supplier for those, but you need to check sensor inputs first.

Unfortunately your hands are largely tied without access to a DRB-3.

WARNING: If your PCM is dropping out shortly after key-on, you are absolutely riding the edge of a full-on PCM meltdown. I strongly suggest leaving the PCM disconnected when you are not actively working on the car until the problem can be verified. PCM meltdown can occur even without the key in position, as they are powered all the time. Cost difference to replace a PCM without a core vs with is huge. Dont risk damage pointlessly while figuring this out.

I disconnected the battery and am going to bring home an oscilloscope from work to look at the output of the crankshaft position sensor and the camshaft position sensor while cranking the engine over. If both of these signals look good, sounds like the next step is to send in my PCM and have you guys take a look.

Good point, Dan.

The Schrader valve port for reading fuel pressure on an early Gen I is at the very rear of the driver side intake manifold... noting that it faces the driver. You might need to remove the windshield cowling to get to the port. It might be helpful to put the gauge on it before and during cranking engine to be sure that you understand just what the fuel pump is doing.

I will check the fuel pressure tomorrow as well, thanks for telling me the location. I am assuming that it’s not just fuel related though as I still have a spark tester inline with the spark plug and still have no sparks or fuel.

 

[99RT10GTS]

Where in PA are you? There is a really good shop in Bath, PA just North of Allentown

 

[Timothy McManus]

I live in State College, do you know if that shop has a DRB3? Sounds like that’s what I need to further diagnose the problem. I could get a trailer to tow it over there.

 

[Bill W]

You could call them. Havik Performance https://www.havikperformance.com/

 

[Timothy McManus]

Ok so I got the scope and it looks like I have good signals on the crank and cam. I took screenshots, yellow is the cam and blue is the crank.

I also took a look at the power to the injectors while cranking. I see voltage and hear the fuel pump when I first turn the key for about 1 second. Then when I crank the engine I will only get power to the injectors for a split second on maybe 1 out of every 5 tries or so. Besides the cam and crank sensors what else is required for the ASD relay to energize? Just want to eliminate all options before I send this thing off to the professionals

 

[Steve-Indy]

As I recall the wording, if the PCM does not receive the appropriate signals from its sensors ( crankshaft, camshaft, upstream O2, MAP) within one second of the engine cranking, the ASD relay will shut off spark and fuel...hence the question that I asked in post #10 of this thread which was: "Have you tried swapping the ASD relay with the starter relay...since you know that the starter relay works ?"