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1978 Seville
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Discussion Starter #1
I have a '78 seville with an EFI 350 V8 that sat for about 6 years. it ran at first, but the fuel was varnished so it ran rough. I replaced all 8 injectors, the fuel pump, fuel filter, spark plugs, and replaced the old gas with new 91 octain. after that it would not start. it would just flood out the car and fill the oil with gas. i then took it to a mechanic, who replaced the distributer and attached pulse sensor, the computer, and spark plugs. It ran great while siting in ther shop. i picked it up today to take it to the exhaust shop since it is missing the exhaust system. I drove it about a mile and it started spiting and sputtering. It eventually died and would not restart. i assume it is flooding again though i haven't investigated. Is it possible that the computer is shorting out? Any idea why it died or what i can test to diagnos? Is switching the car to a carburator a resonable option, $ wise? I already have $1000 invested in the EFI system. its a one owner with 84k (mint) so i am willing to spend more to keep it original. Thanks for looking.
 

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1926 Model T street rod, 2000 Jaguar XJ8, 1999 Corvette.
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6,738 Posts
I would remove the fuel filter and cut it open to see if varnish is present. If it is, the fuel tank must be pulled and cleaned out. This engine had a habit of flooding if the coolant temp sensor failed. The coolant temp sensor sits by the thermostat housing. You can swap the air temp sensor for the coolant temp sensor because they are the same part to confirm repair. The air temp sensor screws into an intake passage at the rear of the intake manifold. The computer was not failure prone. What would fail is where the fuel pump connector was on the computer. Over years, heat from voltage would melt the connector at the computer causing intermittant fuel pump operation or none at all.
 

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1978 Seville
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10 Posts
Discussion Starter #3
thank you for the responce. i'll forward it on to the mechanic and post the results back here. i am glad to here the computer is durable. i think i bought the last used one for sale in the world, and rebuiling them is $350 (rock auto) and requires the old one to be mailed in.

-josh
 

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2001 DTS / 1978 Seville / 1991 Cadillac Brougham
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15 Posts
Hi, the first thing to check if these Seville fuel systems are flooding out is the Fuel Pressure Regulator. One with a ruptured diaphram will cause this problem. I had a 78 that did the exact same thing. Hope this helps.:)
 

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Cadillac 1977 Seville (White) and a Black 2003 CTS
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I have a '78 seville with an EFI 350 V8 that sat for about 6 years. it ran at first, but the fuel was varnished so it ran rough. I replaced all 8 injectors, the fuel pump, fuel filter, spark plugs, and replaced the old gas with new 91 octain. after that it would not start. it would just flood out the car and fill the oil with gas. i then took it to a mechanic, who replaced the distributer and attached pulse sensor, the computer, and spark plugs. It ran great while siting in ther shop. i picked it up today to take it to the exhaust shop since it is missing the exhaust system. I drove it about a mile and it started spiting and sputtering. It eventually died and would not restart. i assume it is flooding again though i haven't investigated. Is it possible that the computer is shorting out? Any idea why it died or what i can test to diagnos? Is switching the car to a carburator a resonable option, $ wise? I already have $1000 invested in the EFI system. its a one owner with 84k (mint) so i am willing to spend more to keep it original. Thanks for looking.
I read somewhere that if the vacuum hose is disconnected at the ??? even momentary it ruptures the diaphram inside the housing causing all kinds of fuel related problems. When I read that article, I was going to print it and keep it with my newly purchased 1977 Seville, I should have eh !
The fellow I bought in from in Toronto also had problems with the injectors (??), but that was chalked up to a dirty gas tank from sitting too long, sounds familiar doesn't it ? I 've only put on about 60 miles (Kingston to Otttawa) since I bought and put it away for the winter.
I was surprised driving it home, I thought it would have a lot more pep for a 350ci w/EFI.
Curious In Ottawa
 

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2005 Cadillac DeVille DTS
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150 Posts
Connect a fuel pressure gauge at the Schrader valve on the fuel rail. At idle, fuel pressure should be 39 PSI. If it's higher, check the return line for blockage, otherwise replace the fuel pressure regulator. If the pressure is too low, check the lines, sock in the fuel tank, chassis mounted fuel pump, and regulator.

Make sure there is manifold vacuum at the fuel pressure regulator.

Also if you pull the vacuum hose off the fuel pressure regulator and fuel comes out, the fuel pressure regulator is defective.
 

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77 seville 81 seville
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1 Posts
[Got mine running ,I am fine tuning now how do you test the pressure regulator JPETRO1051]
what was your problem? I have done just about all of the suggestions except the fuel pressure regulator, and i want to know every possibilty before i continue any advice would be appreciated
 

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I am having the same problem. Got the Seville running after having it parked for years. Removed all gas from the tank. Replaced the spark plugs and changed oil and filter. Got it running and drove the car for several weeks. One day it wouldn't start. So I replaced the distributor cap and rotor. Have since replaced the fuel filter (which was a difficult task). After putting on the new fuel filter it started, ran for half a minute and then died. I did check the resistance on the coolant sensor and it is above 1800. No fuses are blown. It is getting both spark and fuel. What is others experience and what should I do next?
 

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2010 DTS
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87,544 Posts
Put a fuel pressure gauge on the service port on the fuel rail. It's a schreader valve, just like a tire valve. The guage screw on to it.
 

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1926 Model T street rod, 2000 Jaguar XJ8, 1999 Corvette.
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6,738 Posts
This car has 2 fuel pumps both electric. One in the fuel tank, one on the frame rail. Once we know fuel pressure, we can either determine if both pumps are working or not. As a tip, the coolant sensor and air temp sensors are the same part. If the coolant sensor fails, you can swap them to diagnose.
 

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Thanks both of you for your feedback! It is raining here in Seattle so I will wait till the weekend to check the fuel pressure. Should I replace the coolant temperature sensor at the same time? Will it also keep the car from starting?
 

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1926 Model T street rod, 2000 Jaguar XJ8, 1999 Corvette.
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6,738 Posts
The one in the tank is called a "lift" pump. raises the fuel up and out of the tank to the frame rail pump. Common for this car's electrical plug at the back of the ECU to have heat damage and will cause intermittant fuel pump operation. Intermittant voltage to the fuel pump. Running out of fuel will cause the lift pump to fail also. This should have been a new thread rather than a hi jacked 2 year old thread! a failed coolant temp sensor fails electrically open which can flood the engine. I would at least have a new spare one. The distributor also has switches built into the shaft to fire right bank then left bank of injectors. Those switches can wear out or get covered in engine oil.
 

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Picked up the Fuel Pressure Guage and a Coolant Temperature Sensor today. Is there a specific pressure that I need to look for in testing the EFI? Also, does the Air Temperature Sensor control the starting of the engine, or do I just replace the Coolant Temperature Sensor for now?
 
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