still no fspark and no fire from injectors after lots of replacements????? help!

[navyman_98_99]

this is on a 91 q45. I replaced the ecu, the power transistors, the crank angle sensor, the fuel control module and still no spark and the injectors dont fire. the crank angle sensor has continuity to the ecu on all wires. what else causes no spark.I can spray starting fuid in the intake and it starts up for a second then dies. so maybe it is getting spark but it isnt much if it is. I took out the coils and tested them to ground and they dont seem to be getting any spark. fuel pump is new, and fuel filter is new. the fuel pump when first turning on the key you can hear it for about 3 or 4 seconds then it shuts off. same after cranking the engine.So what is next. what can I do next to get this thing running again. I need info to let me know what doesnt cause spark.Thanks Mike

[DAEDALUS]

You seem kind of iffy on the spark. It either has spark or it doesn't. With the ignition on you can check that the coils are getting power from the transistor packs. At least 7 of them should have power, probably all 8. This feeds the primary coils. The ECU breaks power to each coil by way of the transistor packs while the engine is turning. If you have the FSM pay particular attention to diagnostic procedures 6 and 27, in addition to the ignition wiring schematic. If you're certain the injectors are not firing, and if you determine there's no spark, then that would suggest a CAS/harness issue. Have you tried checking diagnostic codes? Also back-probe voltages at the ECU and compare to those in the FSM voltage/pin table.I usually discourage blindly replacing parts, except where there's a strong history and correlation with symptoms.

[navyman_98_99]

Ok, I changed the fuel injectors, the fuel rail and the wiring harness for the injectors today and my injectors still dont fire. I dont get it??? what else would cause my injectors not to fire. I can manually gorund one of the wires to each individual injector then the one I ground, fires. Maybe my ecu's ( I have two of them now) are both messed up. From what I can tell from the schematic is that the ecu tells the injectors to fire, and I have continuity from every ground wire that goes from the injector to the ecu like I should and I have the 12vdc on every injector like I should. So I am not getting the signal from the ecu telling the injectors to fire! What tells the ecu what cylinder is ready for some fuel so the ecu knows when to fire the injectors? I would think the cas but not for sure.any more help would be great!! Thanks Mike

[DAEDALUS]

The CAS is the master clock. It tells the ECU which cylinder is #1 and where the crank is along its rotation to the nearest degree. In the FSM there is a procedure to remove the CAS with the harness still attached and to spin it--you should hear the injectors click as you spin the CAS. How do you know the injectors are not firing while you're cranking the car?Back-probe the ECU connector to get voltages to and from the CAS. Won't validate the part, but it may tell you it's bad.

[navyman_98_99]

have continuity on all the wires going from the sensors to the ecu, all my relays that I can find and that my schematic shows, are all good. I have tons of compression, tons of fuel pressure, my crank angle sensor is reading what it should at the terminals going to the ecu. My injectors still dont fire, unless I manually ground the wire going to the ecu for each individual injector. All I need is fuel to the cylinders, then my car will run again. I have an electrical engineering background and this car has me stumped. I just don't get this dang thing!!!! Any one that has any more ideas, I would love to hear them and try them out, before I take the easy way out and get a diagnostic reading.Thanks every one for the help, I will get this thing going again!!!!Mike

[DAEDALUS]

Seems to be on the input side of things. You have power to the injectors and continuity to the ECU. The only thing I can think of that would shut off the injectors, all else being good, is if the gas pedal was mashed all the way down--bad kick-down switch? There are procedures in the AT section of the manual to do self-diagnostics on the switch. Never done it, and never heard of one failing. It's all I can think of, other than somehow something between the CAS and ECU still isn't functioning.