1994 7.3l hard starting in 40 degree weather
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You need to check your glow plug system. You likely have a bad glow plug relay. Check the hard/no start link in my signature. GP relay testing will be the same, but your truck's wiring to the glow plugs is a bit different with two connectors per bank at the valve cover gasket rather than one as shown in the link.
BTW, your truck should be a Powerstroke, not an IDI. Moved to the correct forum.
Welcome to TheDieselStop
BTW, your truck should be a Powerstroke, not an IDI. Moved to the correct forum.
Welcome to TheDieselStop
Thanks for the help. Also I forgot to say that once it’s been started in the morning I can let it sit for hours and it’ll start up just fine. For example yesterday it took me a while to get it started because I forgot to plug it in but after I got it started and drove it I let it sit for about 8 hours and it started right up.
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Here's the procedures I use for testing:
For checking the injector/glowplug wiring: From each valvecover gasket connection's outermost pins (2 per connector) to ground you should get 0.1 to 2 ohms (indicates good plug and wiring). From each valvecover gasket connection's center pin to each immediately adjacent pin, you should get around 3 ohms (indicates good injector solenoid and wiring). You should not get any continuity from any of the outer pins to the 3 inner pins (indicates no shorts between injector and glowplug wiring). You should also get 0 to 1 ohms from each of the external harness connectors outer pins back to the Glowplug Relay's large terminal on the GP side (indicates good wiring from external connections back to the relay).
To check the glowplug relay (GPR), measure the voltage drop across the GPR's large terminals. While the GPR is active (up to 1.5 to 2 minutes after the key is turned to Wait-to-Start) put your meter leads on the large terminals (one lead on one large terminal and the other lead on the other large terminal). This measures how much voltage is being "lost" across the relay. A reading of 0.3V or more indicates a bad relay. Also, check the relay’s control wires (smaller wires) disconnected from the relay for battery voltage at the Red/Light Green striped wire and ground at the Purple/Orange striped wire (check both when the key is turned to Wait-to-Start).
For a replacement, I like the White-Rodgers 586-902 relay for these trucks. Much better than factory. Cheers!
For checking the injector/glowplug wiring: From each valvecover gasket connection's outermost pins (2 per connector) to ground you should get 0.1 to 2 ohms (indicates good plug and wiring). From each valvecover gasket connection's center pin to each immediately adjacent pin, you should get around 3 ohms (indicates good injector solenoid and wiring). You should not get any continuity from any of the outer pins to the 3 inner pins (indicates no shorts between injector and glowplug wiring). You should also get 0 to 1 ohms from each of the external harness connectors outer pins back to the Glowplug Relay's large terminal on the GP side (indicates good wiring from external connections back to the relay).
To check the glowplug relay (GPR), measure the voltage drop across the GPR's large terminals. While the GPR is active (up to 1.5 to 2 minutes after the key is turned to Wait-to-Start) put your meter leads on the large terminals (one lead on one large terminal and the other lead on the other large terminal). This measures how much voltage is being "lost" across the relay. A reading of 0.3V or more indicates a bad relay. Also, check the relay’s control wires (smaller wires) disconnected from the relay for battery voltage at the Red/Light Green striped wire and ground at the Purple/Orange striped wire (check both when the key is turned to Wait-to-Start).
For a replacement, I like the White-Rodgers 586-902 relay for these trucks. Much better than factory. Cheers!
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