1990 Cadillac Fleetwood fuel injection

Tiny
ROBERTSCHROECK
  • MEMBER
  • 1990 CADILLAC FLEETWOOD
  • 4.5L
  • V8
  • FWD
  • AUTOMATIC
  • 130,000 MILES
Have done a complete tune up all new parts dist, air cleaners, cap, rotor, icm, plugs, wires, even 1 injector,
problem if I prime engine it will start, checked for voltage at injector electrical connectors and I have none maybe.50 volts (digital vom) are the injectors tied to the ecm or the bcm? This engine died a little worse every day till it will not start. Are the injectors triggered by a negative closing at the ecm or bcm or is a positive pulse sent to the injector by the ecm or bcm.

thanks in advance
Robert schroeck 8-22-2014
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Friday, August 22nd, 2014 AT 2:36 PM

6 Replies

Tiny
HMAC300
  • EXPERT
Check fuel pressure first if you have to prime it it's probably low pressure it shold have 40-50 psi with the lower number being minimum. Autoparts rent the gauge. You need a noid light to test to see if injectors are getting power and they shold have 16.2 ohms. The ecm controls the engine/trans, not the bcm. From your description I'd say it's a fuel pressure/volume problem so check that first. If it still will not start check two things, scan for codes, cross A & B on aldl and then if you have anti theft it may be a problem with that.
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Friday, August 22nd, 2014 AT 3:10 PM
Tiny
ROBERTSCHROECK
  • MEMBER
Should have included the fuel pressure is a steady 39 pounds thru the pressure regulator and will climb to 45 pounds if I remove vacuum from the pressure regulator, that should be the norm for starting the engine cold.
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Friday, August 22nd, 2014 AT 4:07 PM
Tiny
ROBERTSCHROECK
  • MEMBER
Also I did reconnect the a and b connectors of the adl and set timing to 10 degrees so that was working, after removing the jumper the timing advanced higher to match RPM. Have removed and replaced timing gear cover etc checked cam and crank for timing mark alignment and it was fine also cylinder was at tdc.
Thanks
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Friday, August 22nd, 2014 AT 4:10 PM
Tiny
HMAC300
  • EXPERT
39psi isn't enough even a pound low will cause problems.
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Friday, August 22nd, 2014 AT 4:50 PM
Tiny
ROBERTSCHROECK
  • MEMBER
I have removed all 8 injectors, yesterday and here is what I did to test them,
i used a 7/16 neoprene fuel line hose that fits the injector fuel inlet very tightly, attached to the other end was a 1/4 nippel that screwed into the hose (air compressor quick connect), both ends also had a worm screw hose clamp tightened to be sure of no leak, all that was left to do was set the air pressure regulator from the compressor to 39 pounds that matched exactly the fuel pump pressure from the cadillac, I then filled the tube and hose that are connected to the fuel injector with penetrating oil till it overflowed I then wiped all excess off, I then pluged in the air supply, all was fine no leak, placed a nice clean sheet of test paper down, then connected negative feed ground to right side pin coming from injector, then touched left side pin which is the 12 volt feed for all injectors to a 12 volt source for a 1/2 second at a time, of 8 injectors all but 1 sprayed a nice clean pattern 1 failed with no pattern at all and was replaced, but from my understanding, it seems that 12 volt should be present always at all the left side pins of all fuel injectors, and that either the ecm or bcm which ever controls the injectors is failing to make the necessary momentary closure to ground to close the circuit that fires that particular injector.
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bob
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Friday, August 22nd, 2014 AT 7:02 PM
Tiny
HMAC300
  • EXPERT
Firt thing injectors don't work off of 12 volts they work off of 5 volts. Secondly I gave you all theinfo on how to test the injectiors in the previous replies. Because your car has an anti theft unit it is probably engaged and not allowing the ecm to turn the fuel on to the injectors. There are two different types on your car pass key and forced entry. Your best bet is to quit messing around with the car and have a pro put a scanner on it to see what is wrong with the anti theft system so your car will start. I have no further comments or suggestions.
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Saturday, August 23rd, 2014 AT 5:53 AM

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