Hard to start after engine warm or parked overnight

[ILIKESHELBYS]

1985 Shelby Charger, 70,000 miles
stock, no fault codes

Symptom #1
After a brief drive, long enough to warm the engine, shut it off to go in the store for about 15-30 minutes and when you return to leave, car turns over fine but will not start easily. I mean it turns over a long time before it starts. Pressing the gas pedal to the floor while it is turning over seems to help and when it fires off, its sputters quite a bit at first, then after a few pats on the pedal it will clear up and run fine.

Symptom #2
After engine warms up, while cruising around town or parking lots, there is a bit of a hesitation when you first step on the gas pedal. This makes the car lurch forward, almost feeling like a buck or that you just got on the gas too hard. If you press the pedal more slowly that you should have to, you dont feel it.

It's got all new tune-up parts, 93 octane that is fresh fuel, fresh filters, new OEM O2 sensor, and the factory ECU. Vacuum harness looks good and tests good.

I am suspecting a leaking fuel injector but Im pretty sure when I built this one I installed new OEM injectors...they sure look new w/o me actually removing them to confirm. Fuel pressure was tested initially and it was at or close to 55lbs (give or take a few pounds) at idle w/the regulator hose attached and the car not under boost.

Anybody had one do something like this? Im wondering if the pedal to the floor is any clue....

thanks in advance for suggestions and tips.

[acannell]

Quote:

Originally Posted by ILIKESHELBYS 1985 Shelby Charger, 70,000 miles stock, no fault codes Symptom #1 After a brief drive, long enough to warm the engine, shut it off to go in the store for about 15-30 minutes and when you return to leave, car turns over fine but will not start easily. I mean it turns over a long time before it starts. Pressing the gas pedal to the floor while it is turning over seems to help and when it fires off, its sputters quite a bit at first, then after a few pats on the pedal it will clear up and run fine. Symptom #2 After engine warms up, while cruising around town or parking lots, there is a bit of a hesitation when you first step on the gas pedal. This makes the car lurch forward, almost feeling like a buck or that you just got on the gas too hard. If you press the pedal more slowly that you should have to, you dont feel it. It's got all new tune-up parts, 93 octane that is fresh fuel, fresh filters, new OEM O2 sensor, and the factory ECU. Vacuum harness looks good and tests good. I am suspecting a leaking fuel injector but Im pretty sure when I built this one I installed new OEM injectors...they sure look new w/o me actually removing them to confirm. Fuel pressure was tested initially and it was at or close to 55lbs (give or take a few pounds) at idle w/the regulator hose attached and the car not under boost. Anybody had one do something like this? Im wondering if the pedal to the floor is any clue.... thanks in advance for suggestions and tips.

how long has it been doing this? im wondering if the plug condition would show any interesting clues..i.e. evidence of running rich , or any other anomolous differences cylinder to cylinder or as a whole

any codes?

[ILIKESHELBYS]

The car had been parked for about a year. I just put a new head and turbo on it as well as freshening up all the normal wear engine items like hoses, belts, tuneup parts etc. So its got new plugs, cap, rotor, filters, engine oil belts and hoses. Its only been running a few weeks and I've put about 500 miles on it since the rebuild/refresh. Also new set of Magnecore wires. Plugs are Champs RN12YC gapped at 35.

stock no fault codes

[4Daytonas]

I suspect you have one or more leaking injectors.Holding to the floor while cranking lets the engine know it's flooded and stops the injector flow. Check your fuel pressure and see if it leaks down when hot./it should not lose pressure while not running.To test you'll have to pull the fuel rail while sitting hot and see if you can see the injector leaking under pressure.Hold the rail over a towel or a container and have an assistant turn on the key to pressurize the system.

[ILIKESHELBYS]

Ahhhhhh. That makes good sense to me. I do plan to pull the fuel rail just as you described to check for a leaky injector...as well as put a gauge on it and see how fast it leaks down. I have confirmed that I have no external leaks causing the pump to have to get the system up to pressure before it can run again. I know there is also a check valve in the 20+ year old pump but I'd say its acting and starting up like it is flooded. It does blow a bit of smoke on that initial startup...dark smoke like pig rich/fuel smoke.

[ILIKESHELBYS]

This turned out to be a leaking fuel pressure regulator. When I pulled the vacuum hose off the regulator I got a spurt of fuel. I know that on the vacuum side there should be no fuel. Replaced w a used one, problem fixed.