Join Date: Dec 2006
Feedback Score: 0 reviews
Re: Glow plugs or Glow Plug Relay
90% of the time, your GPR is gonna be your problem. A quick way to test it is first thing in the morning, using an insolated screw driver etc, jump the two large terminals on the GPR (The relay 4 post solenoid looking device found on the middle/top of the engine, behind the alternator. Keep the jumper on there for apprx 60 sec, and attempt to start. If the vehicle fires up, that is likely your problem.
However, to test it properly, here's what you do. Using a voltmeter, (ensuring the engine is at its coldest condition ie first thing in the morning), with the ignition off, find the two large terminals on the GPR. One will be ground, one will power. Test for a 12V supply voltage at the GPR. By testing across the two large terminals, it should also read 12V ensuring a the GPR has a proper ground.
Now, turn the key into the "RUN" position, and your WAIT TO START light should come on. Test the voltage difference across the two large terminals. They should read somewhere between 0-1 Volt. This means current is flowing thru the GPR to your glow plugs during this time. The WAIT TO START light usually stays on for 16 Sec, (two sec a glow plug), however, after the light goes out the relay can stay on up to 90 sec depending on temp.. If there the voltage difference does not maintain less than 1V for a minimum of 16 sec, your GPR is faulty.
One more test just to ensure it is not the signal the GPR that is at fault, you can also do this. The two smaller terminals are a power signal and a ground for the GPR to transmit power across the two large terminals. Test for a voltage signal when the key is rotated in the the "run" position. This signal is sent from the computer to the GPR. If there is no signal being sent, you then have an issue with the computer or a wiring issue which is extremely uncommon, but all the same, a 1 min test while you are there just to ensure the signal is infact getting to the GPR.
Now a question... Is the signal sent from the computer to the GPR supposed to stay on for the entire time that the GP's are being fired, or is this the job of the GPR internal workings to keep the current flowing to the GP's for a determined amount of time?
96 FORD SUPERCAB, 5"LIFT, 315 BFG M/T'S, 10 000LB WARN WINCH, BUSH BUMPER, GUTTED EBPV, CUSTOM AIR INTAKE, OPEN EXHAUST AFTER DOWNPIPE, UPGRADED IDM, WAITIN FOR $$ FOR MORE MODS.