rempfer
Registered User
This may have been covered elsewhere, but I couldn't find a discussion exactly like this. I apologize if this is a duplicate of another thread.
When I purchased my 1988 F250 4x4 stick shift, except for the wait to start light not staying on very long, the glow plug control circuit seemed to behave okay. The truck didn't start great but didn't appear to have any fuel delivery issue. I tested the existing glow plugs with a multimeter and discovered a couple of bad ones, so I replaced all eight with Motorcraft ZD-9's which I bench tested before installing them. Today, before making this post, I re-tested the glow plugs in the engine and they all are equal at resistance 0.1 and the harness/connectors are clean and in good shape.
Before: When I got the truck with those two bad glow plugs the dash light went out fairly quickly and the relay began to cycle but with several tries one could get the truck started. I think this behavior would be typical under the circumstances.
Now: With all (re-tested) good glow plugs I have the curious behavior that the glow plug light & supplied power seems to turn off before the glow plugs are fully heated. It takes at least three attempts to get the truck started. Interestingly, once the glow plug light turns off one never hears the relay cycle no matter how long one waits to crank the engine.
I think the difficult starting is NOT a fuel supply issue because
(a) once the truck starts it will idle smoothly with no tendency to stutter or die as it might if there were air in the fuel supply,
(b) I have a clear fuel line between the fuel filter housing and the injector return line circuit and no air bubbles appear while the engine is running or when the engine is turned off,
(c) I can repeatedly -- without cranking over the engine -- cycle the key on/off to sort of "ramp up" the glow plug heat and the truck will start more quickly when I eventually do crank it over.
So is it possible that if the glow plug circuit weren't getting enough power that the glow plug power would cycle off before the glow plugs had heated up fully and that the power cycle relay would never engage? If so, where should I look first? If not, what else could be going on?
Thank you,
****
When I purchased my 1988 F250 4x4 stick shift, except for the wait to start light not staying on very long, the glow plug control circuit seemed to behave okay. The truck didn't start great but didn't appear to have any fuel delivery issue. I tested the existing glow plugs with a multimeter and discovered a couple of bad ones, so I replaced all eight with Motorcraft ZD-9's which I bench tested before installing them. Today, before making this post, I re-tested the glow plugs in the engine and they all are equal at resistance 0.1 and the harness/connectors are clean and in good shape.
Before: When I got the truck with those two bad glow plugs the dash light went out fairly quickly and the relay began to cycle but with several tries one could get the truck started. I think this behavior would be typical under the circumstances.
Now: With all (re-tested) good glow plugs I have the curious behavior that the glow plug light & supplied power seems to turn off before the glow plugs are fully heated. It takes at least three attempts to get the truck started. Interestingly, once the glow plug light turns off one never hears the relay cycle no matter how long one waits to crank the engine.
I think the difficult starting is NOT a fuel supply issue because
(a) once the truck starts it will idle smoothly with no tendency to stutter or die as it might if there were air in the fuel supply,
(b) I have a clear fuel line between the fuel filter housing and the injector return line circuit and no air bubbles appear while the engine is running or when the engine is turned off,
(c) I can repeatedly -- without cranking over the engine -- cycle the key on/off to sort of "ramp up" the glow plug heat and the truck will start more quickly when I eventually do crank it over.
So is it possible that if the glow plug circuit weren't getting enough power that the glow plug power would cycle off before the glow plugs had heated up fully and that the power cycle relay would never engage? If so, where should I look first? If not, what else could be going on?
Thank you,
****