Long crank to start

[rjd2]

Hi folks, wondering if anyone has any insight into an issue I have on my DMC-12. At cold, the car takes roughly 15 seconds of cranking to start. I have replaced essentially everything in the fuel delivery system-GM styel fuel pump, hoses, accumulator, filter, etc. I do not believe there is anything in the fuel delivery system that has not been replaced, or sent out for rebuild. Does anyone have any ideas as to where I should investigate? If the car is semi-hot, and I shut it off, it may start on a few seconds of cranking. from dead cold, or dead hot, it will take a minimum of 10 seconds to start. Thanks for any leads!

[Helirich]

Have you put a guage on the fuel line at the warm up regulator? It?s possible that it?s not holding pressure. One thing you could try is to turn the key on, but not crank. The fuel pump will run for a few seconds and stop. Then turn it off and on again. Do this three or four times. Then crank. If it cranks right up, your pressure is bleeding back.

[Bitsyncmaster]

I also agree you need to check your control pressure when engine is cold. It should be around 20 PSI depending on how cold it is. This makes your engine start mixture very rich which is needed to start a cold engine.

You can read the PSI value jumping the fuel pump to run at the RPM relay with your pressure gauge connected. If you start the engine that control pressure increases very quickly to the normal 50 PSI value so it's hard to read an accurate value if you want to calibrate the WUR.

If yours is high, it could be the filter screen in the WUR inlet is plugged.

[rjd2]

Thanks. I'll start there. should my FPG be upstream or downstream of the WUR?

[Bitsyncmaster]

Thanks. I'll start there. should my FPG be upstream or downstream of the WUR?

You measure control pressure tapping into the center line from the FD going to the WUR. You use the same line by shutting off the WUR side for primary pressure but fuel pump is jumpered. You can read primary pressure with engine running tapping into the CSV line or FV line.

[Useight]

Hi folks, wondering if anyone has any insight into an issue I have on my DMC-12. At cold, the car takes roughly 15 seconds of cranking to start. I have replaced essentially everything in the fuel delivery system-GM styel fuel pump, hoses, accumulator, filter, etc. I do not believe there is anything in the fuel delivery system that has not been replaced, or sent out for rebuild. Does anyone have any ideas as to where I should investigate? If the car is semi-hot, and I shut it off, it may start on a few seconds of cranking. from dead cold, or dead hot, it will take a minimum of 10 seconds to start. Thanks for any leads!

My understanding is that it is supposed to take a few seconds before starting. The owners manual says, "Do not operate the starter for longer than 5 or 6 seconds. If the engine does not start wait until the engine has stopped rotating before trying to restart." I've always interpreted that as it can take five or six seconds to start and, if it does take that long, it's not a problem. I don't have any advice for trying to fix it, but I'm just saying you might not need to shave off as many seconds as one might think in order to be back to the normal range.

[Emit]

I rebuilt my car (literally everything), it starts on the turn of the key in all temperatures and all engine phases. If the ignition and fuel system is running in specifications it shouldn't need to be cranking for a few seconds. My one upgrade was Dave Mc RPM relay, rest is stock.

It was a high end car with fuel injection and a bunch of systems to ensure fast and consistent starting, it should start right up.

[82DMC12]

The car is certainly capable of starting on the second or third revolution when cold even if the car hasn't run in a week. A few things I've seen that can affect this:



The female pins on the cold start electrical connector are dirty, full of dielectric grease, or they have been spread apart. Remove the plug, spray with cleaner, and squeeze the pins together with a tiny pick.
Idle motor is not working correctly (doesn't open or close fully)
Vacuum leaks (easy to check with smoke machine)
Incorrect fuel pressure (easy to check with the correct K-Jet fuel pressure gauge)
Ignition system parts are junky , old, etc. Put in a new Bosch rotor, good cap, and top quality wires with Bosch copper plugs
Battery is weak - use a battery switch or put the car on a tender if sitting for more than a week
CO adjustment is not SPOT ON - put a new O2 sensor in and check with dwell meter after a tune-up


I recently went through all this stuff and my car has never started better than it does now.

[Rich]

+1 re the previous 2 posts.

Adding my data to the "It can be done" roster.

Mine's box-stock with zero engine/fuel/ignition mods, now at >90K mi.

Starts up within 1-2 sec under any condition like it always has, including no-surge cold starts. The idle is on spec. Has never failed bi-annual CA smog.

It got its second starter and accumulator about 20 years ago. WUR is original. Still on the OE idle motor after patching a leak at its top near the male plug. Also replaced the failed vacuum delay valve next to WUR and the failed distributor vacuum solenoid within past 4 years.

Plus the regular 30K mile ignition work and O2 sensor replacement by the book. Nowadays I smoke-check for intake vac leaks 2X/year for peace of mind.

You'll figure it out - happy hunting.



The car is certainly capable of starting on the second or third revolution when cold even if the car hasn't run in a week. A few things I've seen that can affect this:



The female pins on the cold start electrical connector are dirty, full of dielectric grease, or they have been spread apart. Remove the plug, spray with cleaner, and squeeze the pins together with a tiny pick.
Idle motor is not working correctly (doesn't open or close fully)
Vacuum leaks (easy to check with smoke machine)
Incorrect fuel pressure (easy to check with the correct K-Jet fuel pressure gauge)
Ignition system parts are junky , old, etc. Put in a new Bosch rotor, good cap, and top quality wires with Bosch copper plugs
Battery is weak - use a battery switch or put the car on a tender if sitting for more than a week
CO adjustment is not SPOT ON - put a new O2 sensor in and check with dwell meter after a tune-up


I recently went through all this stuff and my car has never started better than it does now.

[David T]

It may be time for a tune-up and I would do a smoke test to make sure there are no vacuum leaks. I would also check the Cold Start valve and switch to make sure they are working. If the car has been sitting for a while a cold start could take a few seconds to start till the fuel pump can build up enough pressure to squirt fuel from the cold start valve. Once warmed up it should start quickly.