93 C4 long crank time
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4th Gear
Joined: Jun 2018
Posts: 4
Likes: 0
93 C4 long crank time
My 93 C4 will start instantly when cold , after short run up to temp and a few miles stop and let it sit extended crank and dark exhaust from right side exhaust and rich smell ,and engine stumbles . I am guesssing bad injector leaking and flooding . Any sugestions ?
Melting Slicks
Joined: May 2014
Posts: 2,895
Likes: 592
From: New Port Richey FL
your on the right path, now you need to get a gauge on the test port and prove it or rule it out. As a maintenance item It's good idea to look at the O-2 sensor make sure it's functioning correctly they do have a service life, I have seen many here recommend to replace them like 36,000 to 50,000 miles or every few years.
Last edited by s carter; Dec 28, 2020 at 10:31 PM.
Le Mans Master
Joined: May 2005
Posts: 5,214
Likes: 65
From: Queensland, AUSTRALIA
It will almost certainly be the FPR or a leaking injector.
Pull that vac line off the FPR and see if it is wet, if it is, you may need a new FPR.
While youre at it, hook up a pressure gauge to the fuel rail and turn key to on, watch the pressure come up, and then turn key off. Don't need to start the engine, just let the fuel pump do it's start up cycle. Fuel pressure should hold for a fair while, and it should be around 40-43.5psi.
Safety Car
Joined: Sep 2010
Posts: 3,752
Likes: 190
From: Indiana PA
Are the injectors original? They may be shorting internally, the Multec 1's are known for this. This was the cause of my issues in the past. No conventional testing methods found it but a AMP pattern on a oscilloscope did. Worth checking their resistance with a Multi-meter at least.
ANY FUEL leak from a ruptured FPR would effect ALL engine operation at ALL TIMES on BOTH BANKS. The LT1 intake is open inside of it. A ruptured FPR will put a LOT of fuel into the intake.
Replacing 02's as maintenance is a myth. They may get a bit lazy over time but unless its a problem....not worth it. Mine are original and the car runs perfect, fuel mileage is excellent. It even makes the HP its rated at, the 02's don't do anything at WOT, my point is the engine is healthy.
ANY FUEL leak from a ruptured FPR would effect ALL engine operation at ALL TIMES on BOTH BANKS. The LT1 intake is open inside of it. A ruptured FPR will put a LOT of fuel into the intake.
Replacing 02's as maintenance is a myth. They may get a bit lazy over time but unless its a problem....not worth it. Mine are original and the car runs perfect, fuel mileage is excellent. It even makes the HP its rated at, the 02's don't do anything at WOT, my point is the engine is healthy.
