Expert: Roland Finston - 12/24/2011

Question
no start no fuel prime just a 'CLICK' from fuel pump
no check engine light
repaired ecu power splice
replaced ecu, cam and crank sens, cap, rotor, plugs, wires and coil.
engine light will come on periodically and then i get spark
what is causeing the asd relay to trip?

Answer
Hi Mike,
I haven't obtained manuals for the truck engines so I am flying on the belief that the ignition controls are similar as to those used in the passenger car 4's and 6's of the same time frame. In those, the fuel pump just runs for about a second when the key is turned to 'run' , which may be interpreted as 'click' when you listen. Or it could be the fuel pumps just have different sounds. I would believe that the ecu does turn on the fuel pump but then in the absence of signals from both the cam and crank sesnors it is programmed to have the asd trip off quickly.
So usually if you aren't getting spark when cranking the cause is a failure of one or both sensor signals. Because you have replaced the sensors (and ideally in such a manner as to have the tip of the sensor at the correct distance from the surface it is sensing) then about the only possible reasons for no signal would be that the cam shaft isn't rotating due to a failed timing belt (chains of course are much less likely to fail) or there is a wiring problem between the sensor leads and the pcm. I am not certain why when the c.e.l, ccmes on that you get spark, and other wise not? It almost sounds like the ecu is not working but then when it gets voltage/current is when you get spark. But then you say that you replaced the ecu.
The '92 model year is OBD-I and so you aught to be able to get fault codes using the ignition switch:"on-off-on-off-on and leave on", doing that in 5 seconds or less elapsed time. The check engine light should remain "on" but then begin to flash, pause, flash, etc. Count the number of flashes before each pause. Then repeat the process to be sure of an accurate set of flash counts. Let me know what they are in the order appearance and we'll see what that tells us.
Please let me know if you learn anything useful from my suggestions.
Roland
PS Please 'rate' my answer.