Fluctuating voltage at cold start - PowerStrokeNation : Ford Powerstroke Diesel Forum
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post #1 of 13 (permalink) Old 03-18-2010, 06:46 PM Thread Starter
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Fluctuating voltage at cold start

I will see if I can describe this and have it make sense. On cold startup, to voltage gauge will drop down to about 1/4 up on the voltage gauge when the glow plugs are on. After wait to start light goes off, I start the truck and it starts with no problem. After the truck is running, the voltage gauge will begin to rise up to its normal running location (about 2/3 on the gauge). After a couple of seconds of running, the voltage gauge begins to jump around from 1/2 to 2/3 on the gauge and will do this for a few seconds, then will return back to normal position. There is a slightly noticible difference in engine tone when it is jumping around. The truck has 2 brand new batteries, a new valve cover gasket and one new UVCH because one of the glow plug circuits was fried. I have ohm tested all of the glow plugs at the top side of the harness and all came up at 0.7 ohms. It also has a new alternator, and appears to have a newer GPR. My questions are:

Should it take a few seconds to get up to normal voltage after the truck has fired up? I am used to seeing the voltage gauge jump right to its normal reading immediately after the truck has been started (this has been my experience on my other powerstrokes).

Is this jumping around of the voltage gauge the glow plugs cycling on and off? I thought when they cycled on and off they would stay on for a few seconds then turn off and back and forth. This voltage fluctuation is about every second.

If this is how the glow plugs cycle, should there be such a draw that I can see it on the voltage gauge when the truck is running?

If I need to make a short video, I can do it if I didn't make sense with my description above.

Thanks fellas

Dave

99.5 F250 Lariat : 6" lift on 37" Toyo MT's, DP Tunes, Built Transmission, Airbags, AIH Delete, 38R, Banks Big Head, CCV Mod, Sinister Regulated Return, IH bellowed up pipes, AFE Stage II, ISSPro Performax gauges, Scan Gauge, Casserly Stage I's, T-500 HPOP, Swamp's IDM
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post #2 of 13 (permalink) Old 03-18-2010, 07:12 PM Thread Starter
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Re: Fluctuating voltage at cold start

Here is a video

Voltage gauge.AVI videos from trucks videos on webshots

Dave

99.5 F250 Lariat : 6" lift on 37" Toyo MT's, DP Tunes, Built Transmission, Airbags, AIH Delete, 38R, Banks Big Head, CCV Mod, Sinister Regulated Return, IH bellowed up pipes, AFE Stage II, ISSPro Performax gauges, Scan Gauge, Casserly Stage I's, T-500 HPOP, Swamp's IDM
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post #3 of 13 (permalink) Old 03-19-2010, 03:05 AM
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Re: Fluctuating voltage at cold start

Check out your GPR, it could be the cause.

Bryan

97 F250 SC LB 4x4 Auto 368,000 miles, AD's, 3in down pipe, Straight Pipe,EBPV deleted, DIY Intake, Racer X converter and valve body, Beans tunes
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post #4 of 13 (permalink) Old 03-19-2010, 06:24 AM Thread Starter
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Re: Fluctuating voltage at cold start

The GPR is fairly new and the system is functioning. What should I check out on the GPR? Is there a spec for voltage drop across the big leads?

Dave

99.5 F250 Lariat : 6" lift on 37" Toyo MT's, DP Tunes, Built Transmission, Airbags, AIH Delete, 38R, Banks Big Head, CCV Mod, Sinister Regulated Return, IH bellowed up pipes, AFE Stage II, ISSPro Performax gauges, Scan Gauge, Casserly Stage I's, T-500 HPOP, Swamp's IDM
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post #5 of 13 (permalink) Old 03-20-2010, 04:52 PM
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Re: Fluctuating voltage at cold start

Mine will hang around 1/3 for 30-60 sec after startup then jump to normal. however if I put it in gear and start accelerating during that time it will jump as you are describing so I just let her sit til it is up to normal then it will stay there.

1997 F350 PSD, 308,000mi, 4:10's, 4.0" strait exhaust from dp back to single 5" Stack, superchips 1705, 4R100 trans. 315/75r16 Dick Cepek Mud Countrys
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post #6 of 13 (permalink) Old 03-20-2010, 06:38 PM
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Re: Fluctuating voltage at cold start

That doesn't seem normal. I'd have the alternator checked.

'97 SCLB 4x4, 3.55, D60 w/ TrueTrac, 6637, Banks Techni-cooler, BTS Trans, Tru-Cool 4921 Trans Cooler, 1.0 exhaust housing, no ebv, 3" DP, Straight Exhaust, E-Fuel, TW tunes, International WP, 203*, Isspro Gauges
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post #7 of 13 (permalink) Old 03-22-2010, 01:55 AM
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Re: Fluctuating voltage at cold start

i have this issue also, what is the GPR
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post #8 of 13 (permalink) Old 03-22-2010, 02:07 AM
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Re: Fluctuating voltage at cold start

Quote:
Originally Posted by 4doorshortbox View Post
i have this issue also, what is the GPR
Glow Plug Relay

'97 SCLB 4x4, 3.55, D60 w/ TrueTrac, 6637, Banks Techni-cooler, BTS Trans, Tru-Cool 4921 Trans Cooler, 1.0 exhaust housing, no ebv, 3" DP, Straight Exhaust, E-Fuel, TW tunes, International WP, 203*, Isspro Gauges
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post #9 of 13 (permalink) Old 03-10-2016, 10:33 PM
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Re: Fluctuating voltage at cold start

Did anyone solve this? I have the same issue. I installed a new alternator and GPR.

Thanks
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post #10 of 13 (permalink) Old 03-10-2016, 11:19 PM
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Re: Fluctuating voltage at cold start

Quote:
Originally Posted by MacG22 View Post
Did anyone solve this? I have the same issue. I installed a new alternator and GPR.

Thanks
What issue? The voltage bouncing around or a lower voltage for about 1-2 minutes?

96 F250 XLT 4x4, 4:10 gears, 5 speed, Tymar intake and HX hose, downpipe, pyro and boost guages, coolant filter, Luc clutch
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