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I purchased a 1979 Coupe deVille with the optional fuel-injected 425. I bought the car, non-running, because it had Dayton knock-off wire wheels on it, easily worth more than the whole car. After my shop replaced both fuel pumps and performed a tune up (wires, cap, plugs, all filters, etc.), it fired right up, but turns off after a couple of miles of driving, when warm. Restarts when cold again. My shop knows nothing about the first year Cadillac fuel injection, but I suspect the fuel pump relay or timer, if there is one in the system. OEM fuel pumps were the same as used on early Volvos and BMWs. Anyone an expert on this f.i. system? My ultimate goal is to pass CA smog, so I have to get it running perfectly. With the new exhaust, radiator, heater core, and upcoming leather interior, paint, and tires, I've too much invested to stop now!
 

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70 Deville 77 Fleet 78 Seville 92 Deville 03 Deville
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Well, you should check the fuel pressure when it dies to verify if it is a lack of fuel or possibly lack of spark. I think the fuel pump gets it's signal(?) from the ECU so you might want to watch Ebay in case a used ECM comes along. A factory service manual would be very valuable to troubleshoot that system; those are on Ebay too.
 

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95 FWB 81SDV 96 FWB 94 Fleetwood
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I have the 79 shop manual and might be able to help...two thing to do to get us going in the right direction...first , when its cold...there are two sensors , one for coolant and one for air temp..check the ohms in each....the sensors are the same...look for the coolant sensor in a hose at the back of the passnger side head...I know some were there, but not sure if your year is also... the air temp sensor is in the intake manifold.... back secton on passanger side... when cold these sensors should be about the same ohmage..+ or - a 100 ohms... when they go bad they check open..okay if they check good ...... after it stalls and don't restart.... pour some gas in the throttle body and see if it starts...answer to these questions will get us going in the right direction...
 

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Eldorado
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If all the other ideas didn't fix it, you might want your ECU tested out. I can do that for cost of postage of you like (see on photobucket, find user bcroe)

Bruce Roe CLC Advisor #14630
 

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1926 Model T street rod, 2000 Jaguar XJ8, 1999 Corvette.
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The coolant temp sensor is located next to the thermostat housing (driver side?), and yes its the same as the air temp sensor. When they fail they provide a very rich mixture and will flood a warm engine. Simply swap the 2 sensors and see if the problem goes away. If so, replace the swapped air temp sensor. The air temp one is in the intake air runner at the rear of the manifold. This car also had a tendancy to melt the fuel pump signal wiring at the back of the ecu. Causing it to be loose on the connector possibly causing the pump to intermittantly quit. Locate the ecu, unplug the multi wire connector and look very closely at the socket end. Any signs of melted plastic? If so, sometimes cutting that wire out of the multi wire plug and installing another connector on that wire will provide a more secure connection. Idle speed which must be under 1000 rpm to pass a smog test is controled by a large single air screw at the front center of the throttle body.
 

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I have shown on PHOTOBUCKET (user bcroe) how to avoid failures due to overloaded relay/connector/ECU wires in the fuel pump circuit.

Bruce Roe CLC advisor #14630
 
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