1993 Dodge Spirit long crank on hot re start

DDEC4

MEMBER
1993 DODGE SPIRIT
6 CYL
FWD
AUTOMATIC
192,000 MILES

Car is well maintained, total engine rebuild at 189000
new parts included:
E.G.R. Valve
Map Sensor
I.A.C. Motor
Six New Injectors, Fuel Pump & Pressure regulator
Coolant temp. Sensor
Dist Cap, Rotor, wires, plugs air and gas Filter
timing Belt & tensioner
Complete exhaust system including Catalyst

Defect: when cold engine statrs and idles fine, no
drivability problems at all cold or at operating temp
if I shut down the engine for 15 -30 minutes and try
to restart engine will crank for 10 - 15 seconds before starting, if I press on the accelerator 1/4 to
1/2 throttle crank time is shortend, hooked up a
pressure guage, feul pressure is 39 pounds steady
at Idle, when shutting off engine pressure slightly drops (37 lbs.), After 30 mins, pressure is at 33 lbs,
turned ignition on, pressure rose to 40 lbs. Cranked
engine, still long crank before starting, only if I give
some throttle will it start normal.
Suggestions?

1 Reply

CARADIODOC

MECHANIC
33,737 POSTS

Sounds like the fuel supply system is working properly. When you turn on the ignition switch, the fuel pump will run for only one to two seconds, then turn off until the engine is rotating, (cranking or running). This insures fuel pressure is up in preparation for starting. That's the 40 psi you're seeing.

Two forces act on the fuel molecules to pull them through the injector nozzles, fuel pressure and engine vacuum. To maintain a steady fuel / air mixture, when vacuum goes up, as when the engine is running, fuel pressure goes down, so the net effect on the fuel is the same. That's why pressure is lower when the engine is running, and it stays there after you stop the engine.

Dropping a few more pounds in a half hour suggests the possibility of a leaking injector leading to a flooded condition. I have the same situation with my '88 Grand Caravan with the 3.0L engine. The crank time when warm is only about three to five seconds, but I suspect an injector is the cause. After it sits long enough to cool down, the fuel probably condenses or evaporates so the problem doesn't show up.

What you might try is to stop the warm engine by removing the fuel pump relay or fuse. The injectors will continue to bleed off pressure until the engine can't run any longer. Once it stalls, turn the ignition switch off, THEN put the relay or fuse back in. This will cause a much lower pressure in the fuel supply line and less leakage from an injector. Wait the necessary 15 - 30 minutes, then try starting the engine. Since you have the luxury of a pressure gauge, be sure the pressure comes up to 40 psi before cranking. If it doesn't reach 40 psi, turn the ignition switch back off, wait a few seconds, then turn it on again. Each time you do that, the fuel pump will run for a couple of seconds. It rarely takes more than two cycles to get the pressure up for starting.

Don't kill the engine by removing the Automatic Shutdown (ASD) relay. It will turn off power to the fuel pump too, but it will also kill the spark and the injectors just the same as if you turned off the ignition switch, so it won't prove anything.

Caradiodoc