View Full Version : Car will not start, backfired smoke form under hood on pass. side

09-28-08, 03:44 PM
My 1997 deville with 140k, well maintained...will not start. It backfired and smoke came out from the pass. side of the engine. I tried it again and it did the same thing. Any help??

09-28-08, 04:13 PM
It sounds as if the intake manifold overpressure valve is unseated, causing a vacuum leak lean backfire. After a couple of those I would get a set of intake manifold gaskets, remove the manifold and check it as well as all the vacuum hoses and fittings from the throttlebody and cam covers. Quite a few posts lately concerning intake manifold work, some with pictures. Look here and in Deville.

09-28-08, 04:39 PM
Are the plugs & wires original? Has the fuel rail recall been done? Have you checked the FPR to see if it's leaking?

09-28-08, 05:02 PM
Thanks for the info and quick replys...I am learning to navigate the site as I am a new user!
I replaced plugs and wires last year along with the recall. Looks like R&R the intake is my next step! I agree with the possable pressure valve problem....
Is this a mechanical issue? And replacing the valve should fix it.....I did replace the starter last year...so still familar with removal of intake..
Thanks,:thumbsup: let you know

09-28-08, 05:10 PM
You might find a misplaced intake gasket....... the bolt torque is 7.5 ft/lb, not very tight. Check the injector O-ring seals. The overpressure valve is either a spring loaded flap or mushroom. Check the operation and seat. Look in recent Seville, Deville, and Northstar Performance threads for the correct coil-to-plug wiring diagram. I have posted several in the last 2 weeks. The wire connection is critical in order to avoid a nagging low-speed miss.

09-28-08, 06:22 PM
You didn't mention the FPR. If it is leaking, it will bleed off fuel pressure after shut down and you'll have raw fuel sitting in the vacuum line and manifold. That might be the cause of you backfire. Check the FPR first as it is very easy. It is a small canister on the fuel rail with a vacuum line on top. Just pull the vacuum line at idle and look for fuel leaking from the nipple. There should be none.

09-28-08, 09:25 PM
Thanks again.....
The FPR.....that may make sense because the engine did (before the backfire) turn over for 5-10 seconds before it would fire....This would have to checked after the cause of the no-start is corrected..

Or was this the cause of the initial backfire....damaging the pressure valve?
I'am sure pulling the intake and checking the valve,gaskets and intake and possabliy replacing the FPR is a good bet.

10-01-08, 02:25 PM
:worship: Does anyone have OEM part #'s for..
FPR and
Manifold overpressure valve
1997 deville?

10-01-08, 05:56 PM
The FPR can come from www.rockauto.com. Or both can come from Luke in parts at Lindsay Cadillac, M-F, 9-5 EDT --------> over there, or www.gmpartsdirect.com or www.gmotors.com.

10-08-08, 08:22 PM
Okay...........I removed the intake..check the overpressure valve which looks good and seated..the intake gasket looked good and appears to have been sealed and okay.. along with an inspection of the intake...thats loooks good too. It does seem do been loaded with gas...I cleaned and are read for reasembley....Any suggestion before?

10-08-08, 08:45 PM
Install the manifold and torque the bolts to 7.5 - 8 ft/lb. Connect and check everything, including the vacuum connections, but leave the fuel rail/injectors hanging over the engine. Have an assistant turn the key to RUN but not START. You may have to do this 3 times with 30 seconds between tries in order to bring fuel pressure up in the system. If any fuel injector is leaking it will spray or drip. That will be your gas in the manifold source. If no leaks, rub a tad of engine oil around each fuel injector base O-ring and replace the system. Start up and drive.

We seem to be in the fuel injector diagnosis mode this week..........:confused:

Keep a big HALON fire extinguisher in the garage......good for insurance; yours and the house.

10-08-08, 09:05 PM
How about the FPR? Did you check it? Was it leaking?

10-14-08, 06:07 PM
Okay guys.....Followed instructions for installation. Did not see any defective injectors. So I did get the engine running and took it on a beat run! Well it performed good. Still getting long cranks before she fires.(scary) So I will replace the FPR.............I assume that will help...even the the test did not come up with fuel!!:yup: