Continuity between glow plug line and ground? - Diesel Forum - TheDieselStop.com
'99 & up 7.3L Power Stroke Engine and Drivetrain Discussion of the '99 & up 7.3L Power Stroke diesel engine and drivetrain in the 1999-Up Super Duty trucks and Excursions. No gas engine discussion allowed except on transmissions and drivetrain that pertain to all models. Please confine discussion of topics in this forum to those items that are specific to the 7.3L Power Stroke engine.

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post #1 of 13 (permalink) Old 05-30-2018, 09:42 PM Thread Starter
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Continuity between glow plug line and ground?

i'm trying to diagnose some electrical issues (after replacing dead batteries, now the whole electrical system is dead)
one thing i noticed is i have continuity between the line from the GPR and ground, i would think maybe some but there should be some high resistance because of the glow plugs right?
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post #2 of 13 (permalink) Old 05-31-2018, 07:51 AM
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Are you measuring the battery side of the GPR or the glow plug side? If it's the glow plug side, then you should see resistance. That's because the glow plugs are resistive heaters. Are you getting any activity after the battery swap? Will the headlights turn on?

2003 F-250 XLT Crew Cab 7.3L, Chrome BigTex Grille Guard, Quad pillar - 3 ISSPRO gauges (trans, pyro, boost) and DP-Tuner F6; Roush fuel pressure / temperature / oil pressure gauges, Ford Severe Duty AIS, 31 row 6.0 transmission cooler, ScanGauge II, Marinco mod, Walker BTM

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post #3 of 13 (permalink) Old 05-31-2018, 07:59 AM Thread Starter
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Are you measuring the battery side of the GPR or the glow plug side? If it's the glow plug side, then you should see resistance. That's because the glow plugs are resistive heaters. Are you getting any activity after the battery swap? Will the headlights turn on?
continuity from the glow plug side to ground
after putting in new batteries everything died. no crank, no lights, nothing
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post #4 of 13 (permalink) Old 05-31-2018, 10:12 AM
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If you have no lights, you’ve got a battery connection issue. That circuit doesn’t go through the computer or ignition.


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2003 F-250 XLT Crew Cab 7.3L, Chrome BigTex Grille Guard, Quad pillar - 3 ISSPRO gauges (trans, pyro, boost) and DP-Tuner F6; Roush fuel pressure / temperature / oil pressure gauges, Ford Severe Duty AIS, 31 row 6.0 transmission cooler, ScanGauge II, Marinco mod, Walker BTM

I wonder if clouds ever look down on us and say, "Hey, look - that one is shaped like an idiot!"
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post #5 of 13 (permalink) Old 05-31-2018, 10:34 AM Thread Starter
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If you have no lights, you’ve got a battery connection issue. That circuit doesn’t go through the computer or ignition.


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yes sir, thank you. i would agree
my concern now, is how much resistance should i see between the ring terminals (on the glow plug side) and the ground? i'm concerned there could be something wrong on the glow plug side.
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post #6 of 13 (permalink) Old 05-31-2018, 11:12 AM
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Since the glow plugs are wired in series (not parallel), the resistance would be cumulative. The normal glow plug resistance range is 0.6-2.0 ohms. You have 8 glow plugs. Assuming they are all working, you should have between 4.8 and 16.0 ohms.

2003 F-250 XLT Crew Cab 7.3L, Chrome BigTex Grille Guard, Quad pillar - 3 ISSPRO gauges (trans, pyro, boost) and DP-Tuner F6; Roush fuel pressure / temperature / oil pressure gauges, Ford Severe Duty AIS, 31 row 6.0 transmission cooler, ScanGauge II, Marinco mod, Walker BTM

I wonder if clouds ever look down on us and say, "Hey, look - that one is shaped like an idiot!"
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post #7 of 13 (permalink) Old 05-31-2018, 11:42 AM
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Quote:
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Since the glow plugs are wired in series (not parallel), the resistance would be cumulative. The normal glow plug resistance range is 0.6-2.0 ohms. You have 8 glow plugs. Assuming they are all working, you should have between 4.8 and 16.0 ohms.

Actually the glow plugs are wired in parallel. Series would be connecting one glow plug + side to the next glow plugs - side and the rest the same way.



Parallel is wiring the + side of all the glow plugs together with their - sides being the ground.



But I don't believe that the problem is the glow plugs but something else unless the OP changed out the relay to a case grounded relay which would put the glow plugs on 100% of the time that the key is on.

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post #8 of 13 (permalink) Old 05-31-2018, 12:00 PM
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To clarify it a little bit more to find the resistance of a series circuit you would add the resistance of glow plug 1+ glow plug 2+ glow plug 3 and so on.

To find the total resistance for a parallel circuit is a little bit more complicated.

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post #9 of 13 (permalink) Old 05-31-2018, 01:26 PM
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1/(1/R1+1/R2=etc) - that would lend a value of 0.075 to 0.25.

Must have been half asleep earlier...
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I wonder if clouds ever look down on us and say, "Hey, look - that one is shaped like an idiot!"
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post #10 of 13 (permalink) Old 05-31-2018, 09:43 PM
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1/(1/R1+1/R2=etc) - that would lend a value of 0.075 to 0.25.

Must have been half asleep earlier...
You been out in the sun too long?

As for the no power thing, don't forget the fuse links, but if those are opened, I would be checking to see why.

Was there ANY life when you installed the batteries, or did nothing work right from the get-go?

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post #11 of 13 (permalink) Old 06-02-2018, 07:29 PM Thread Starter
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i figured out why i had no electrical, the connection on the driver side fender rusted through. i have replaced it this morning and i've got power again

but still cannot get torque pro to communicate with my ECU. i can hear my fuel pump, and most lights (ABS, glow plug, etc, and etc) are lit up on my dash in the key on / engine off position. something is not right.
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post #12 of 13 (permalink) Old 06-02-2018, 08:12 PM
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Check the cigarette lighter fuse.


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2003 F-250 XLT Crew Cab 7.3L, Chrome BigTex Grille Guard, Quad pillar - 3 ISSPRO gauges (trans, pyro, boost) and DP-Tuner F6; Roush fuel pressure / temperature / oil pressure gauges, Ford Severe Duty AIS, 31 row 6.0 transmission cooler, ScanGauge II, Marinco mod, Walker BTM

I wonder if clouds ever look down on us and say, "Hey, look - that one is shaped like an idiot!"
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post #13 of 13 (permalink) Old 06-03-2018, 02:09 PM Thread Starter
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Check the cigarette lighter fuse.


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thank you sir. i've checked that, fuse is good. i also checked any fuse that appears it could be remotely related.
plus i've systemically disconnected the Intake Air Heater, Fuel Bowl heater, and the Exhaust Back Pressure Valve and after each was disconnected i checked again.
it seems when i go from key off, to key on after it sits for a couple of minutes it appears i can connect to the ECU long enough to scan for fault codes (first thing i do every time) but when i go back into Torque Pro for monitoring it looses connection. I'm not sure if it's just timing or if it's actually something to do with the connection.

I'm going to start testing relays next. any other ideas please?...
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