How much voltage drop do/should the glow plugs cause?

[BigRedWeather]

A second or two after I turn the key on on my 97 F350 the voltage drops from 12.8 to 9.8. That is right when the glow plugs should be fired for roughly 45 seconds. Is my voltage drop acceptable or should I be looking for another problem?


Thanks,


BigRedWeather

 

[sassyrel]

A second or two after I turn the key on on my 97 F350 the voltage drops from 12.8 to 9.8. That is right when the glow plugs should be fired for roughly 45 seconds. Is my voltage drop acceptable or should I be looking for another problem?


Thanks,


BigRedWeather

acceptable...might be as long as 2 minutes before the amp gauge goes to where it will normally sit........

 

[madpogue]

Depends on how you're measuring it. Check the voltage on BOTH large terminals of the relay, WHILE the GPs are running. If the DIFFERENCE is more then 0.3V, the relay is faulty. More generally, less than 10V is on the low side. Have you LOAD tested the batteries?

(The truck has a voltmeter, not an ammeter, BTW.)

 

[OLDBULL8]

Takes about 2 seconds to drop to that voltage from 12.5 to 9.5, that's acceptable. Your pulling about ~196 amps which drops to ~130 during the GP cycle. GP cycle is normally ~15 seconds then you get up to an ON/OFF relay cycle up to 2 Minutes. All this when temp is around 50*F or below with a cold engine. The PSD's have a totally different controller than the IDI's. The ZD11 is the same as the ZD9 as far as current pull, there just little longer in length.

 

[madpogue]

Takes about 2 seconds to drop to that voltage from 12.5 to 9.5, that's acceptable. Your pulling about ~196 amps which drops to ~130 during the GP cycle. GP cycle is normally ~15 seconds then you get up to an ON/OFF relay cycle up to 2 Minutes.

NO. If the glow plugs "cycle" at all, that is, if they go on and off, something is WRONG. The PCM sets the GP run time (anywhere from a few seconds up to two minutes) based on EOT when you first turn the key to RUN. They should stay ON for that entire time. If the relay clicks on and off more than once, that indicates an excessive drop in voltage, resulting in power loss to the PCM.

The PSD's have a totally different controller than the IDI's.

The PSDs don't have a contoller at all.

 

[OLDBULL8]

The PSDs don't have a contoller at all.

What kind of a PSD do you have that don't have one?

 

[madpogue]

What kind of a PSD do you have that don't have one?

Both our '95s. Work like EVERY PSD. Run time is set by the PCM.

 

[trackspeeder]

97 Cali and all 7.3 Excursions use a GPCM to control smoke. All other PSD's rely on the PCM to control the relay. Which could cycle for up to 2 minutes to control smoke.

 

[OLDBULL8]

The PSD's have a totally different controller than the IDI's. The ZD11 is the same as the ZD9 as far as current pull, there just little longer in length.

Guess I should have been more specific and said by the PCM and/or a GPCM. Sorry about that.

 

[sassyrel]

Guess I should have been more specific and said by the PCM and/or a GPCM. Sorry about that.

no need for sorry at all,,i understood perfectly what you were talking about.................

 

[trackspeeder]

no need for sorry at all,,i understood perfectly what you were talking about.................

So did I.

 

[XOLATEM]

I just learned something...even though I probably will '('never')' own a PSD...but it is good to have a little insight into how they work...

I worked at a place that had an early 6.0 and we had to keep the block warmer plugged in all of the time...

So...thank you guys in retrospect for the info...I appreciate it...