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Ivan, ASE Certified Master Technican
Category: Cadillac
Satisfied Customers: 4871
Experience:  ASE Master Tech w/ 20+ years in the field. Self employed for 9 years. Member of AUTOLAB radio show.
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my 91 Cadillac Deville dies while driving down the road, then

Resolved Question:

my 91 Cadillac Deville dies while driving down the road, then will restart after 10 or 15 minutes, there is no ryme or reason to when it will stall.   
I put in a new fuel pump but no change . someone said to change the fuel pump relay
can you help?
Submitted: 8 years ago.
Category: Cadillac
Expert:  Ivan replied 8 years ago.

HelloCustomer For the car to stall, you are either losing fuel to the engine or spark at the spark plugs. Before you replace anything else, let's figure out what we are losing. This is the first thing I want you to do. Keep a can of carburetor cleaner in the car with you, When the car stalls, try to restart, if it doesn't start, Take the air snorkel off of the top of the throttlebody, Spray a liberal amount of carb cleaner into the throttle body. Try to start the car, see if it tries to start. Any signs of life are what we are trying to see here. If it stumbles and stalls or starts for a second, we can assume it has spark and fuel is our issue. If it does not make any change at all, remove one spark plug wire, insert a screwdriver into the end and place it near a metallic surface. You may need a second person if you can't position this so you can see it. Crank the engine, is there good blue spark. Let's start with these tests first. Let me know what you find and we'll continue with the next steps.


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Customer: replied 8 years ago.
I did what you said and when the car stalled I sprayed some starting fluid in the throttle body and the car started and continued to run , sometimes when I turn it off when it is hot ir will not restart until it cools off
Expert:  Ivan replied 8 years ago.
Ok, let's see if that is the norm. Give it a few more times to stall or not start and let's see if it restarts with carb cleaner every time. Try to verify it won't restart just prior to spraying. Let's make sure this is predictable. If it works everytime, we are going to focus on fuel pressure and fuel delivery. Keep me posted. Let's find out at least one more time stalling and one hot no start .
Customer: replied 8 years ago.
<p>it started the first time and drove 25 mi. (40 mins)</p><p>turned it of at wal mart </p><p>it started when I came out and went 1/4 mile and died after starving for fuel</p><p>waited 30 mins </p><p>started it with ether </p><p>went another mile & it died</p><p>waited 20 mins & started it again with a shot of ether </p><p>went 1/2 mile & it died again </p><p>and so on and so forth 2 more times until I made it home</p>
Expert:  Ivan replied 8 years ago.

Ok, that pretty much makes me feel confident that we have a fuel issue. I think we are dealing with a fuel pump. Your engine has a fuel pressure test fitting on the fuel rail, let's get a fuel pressure guage on this vehicle. Tape it to the winshield and go for a ride. Let's make sure fuel pressure is dropping when these episodes occur. If so, I want to verify power to the fuel pump when the car is dead. If so, we are going to look at this fuel pump and fuel filter. If fuel pressure remains high, we are going to focus on fuel injector pulse. The fuel pressure you should find is:


Ignition ON Engine OFF 40 - 50 psi
Idling With Vacuum hose Connected To Regulator 32 - 38 psi

Customer: replied 8 years ago.
i understand everything you said except where to find the connection for the pressure guage and the part where you said
"Idling with Vacuum hose connected to regulator"
Customer: replied 8 years ago.
where do I connect the pressure guage , and what do you mean by "Idling with Vaccum hose Connected to Regulator" ?
Expert:  Ivan replied 8 years ago.

At the fuel pressure regulator you will find a vacuum line connected to it. This is where you would either disconnect or reconnect the vacuum hose. Here are two pictures to help you find it.




Here is the location of the test port. It's under this cap.