high pressure oil pump???
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Freshman User
Joined: Jun 2009
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high pressure oil pump???
My 94 7.3 runs rough when first started and runs that way until it warms up....Can plug truck up and when started the next morning it runs like a champ. I believe all the glow plugs are fine. I had to replace the valve cover gasket and harness plugs on the right bank of the motor. I was wondering if it might have something to do with high pressure pump loosing prime??? The guy I bought the truck from said something about a check valve or something.. Any Ideas... I should not have to be plugging the truck during 100 degree weather. Thanks for any input.
Post Fiend
Joined: Mar 2007
Posts: 9,010
Likes: 5
From: Johnson City, TN.
If you are plugging the truck in all you are doing is heating it up. While there is a possibility the pump could maybe cause this I would first investigate the GP's. It is easy and quick with an ohm meter.
Ohme the outer contact to the middle contact.Ie:.
G I O I G
Whereas "G" is the glow glug and "O" is the ground. I believe somewhere around 1.2 is normal.
Ohme the outer contact to the middle contact.Ie:.
G I O I G
Whereas "G" is the glow glug and "O" is the ground. I believe somewhere around 1.2 is normal.
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Freshman User
Joined: Jun 2009
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When I first got the truck we checked them through the valve cover gasket with a test light.with the light clamped to positive it lit up when the prongs in the gasket were probed. But I haven't pulled them out individually and ohmed them. Will do when I get a chance. Thanks.
Post Fiend
Joined: Oct 2003
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From: MICHIGAN
You can ohm them through the valve cover gasket. Anything more than 3 ohms it is getting weak and will not get hot...right away.
Are you starting the engine immediately after the Wait to Start (WTS) light goes out? The WTS light will go out after 10 seconds or so but the GP's are still activated...for up to 2 minutes depending on the ambient temperature.
Your next cold start, try waiting for 30-60 seconds before starting it. If the idle is better then you have a couple weak GP's.
Are you starting the engine immediately after the Wait to Start (WTS) light goes out? The WTS light will go out after 10 seconds or so but the GP's are still activated...for up to 2 minutes depending on the ambient temperature.
Your next cold start, try waiting for 30-60 seconds before starting it. If the idle is better then you have a couple weak GP's.
Fleet Owner
Joined: Aug 2004
Posts: 20,419
Likes: 197
From: AZ
No, do it like Neal said. If you motor starts right up when plugged in then its not your HPOP leaking down. I go with the above, some GP's are out or getting weak.
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Freshman User
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When gp are ohmed while still installed where would be the best place to touch the meter probe that is not touching the valve cover gasket?
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Fleet Owner
Joined: Aug 2004
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From: AZ
Post #2 above by Neal explains where to touch your meter probe. Unplug the connectors (four of them, two on each value cover) and on the value cover side of the unplugged connector you see five pins. The middle one is ground, touch that while touching the outside pin to check one GP. Repeat for the other outside pin while still holding the one meter probe to the middle pin (ground). I once stated that I just pull the value cover off, pull the GP's out and put jumber cables to them. If they glow red hot, there good. If they don't, replace that one. This statement got a lot of laughs from the forum. I was told to join the 20th century, lol. Ohm method is a lot easier!
Post Fiend
Joined: Oct 2003
Posts: 5,903
Likes: 1
From: MICHIGAN
If you use the center pin for ground the ohm reading should be higher. That is the ground for the injectors, going though the IDM and all the associated wiring. The GP's get their ground when screwed into the head.
IMO, It's better to clamp it to a clean ground on the engine block or the battery ground (-). Makes it a little less cumbersome too.... there isn't a lot of room in the connector for both probes.
IMO, It's better to clamp it to a clean ground on the engine block or the battery ground (-). Makes it a little less cumbersome too.... there isn't a lot of room in the connector for both probes.
Fleet Owner
Joined: Aug 2004
Posts: 20,419
Likes: 197
From: AZ
If you use the center pin for ground the ohm reading should be higher. That is the ground for the injectors, going though the IDM and all the associated wiring. The GP's get their ground when screwed into the head.
IMO, It's better to clamp it to a clean ground on the engine block or the battery ground (-). Makes it a little less cumbersome too.... there isn't a lot of room in the connector for both probes.
IMO, It's better to clamp it to a clean ground on the engine block or the battery ground (-). Makes it a little less cumbersome too.... there isn't a lot of room in the connector for both probes.
Senior User
Joined: Dec 2008
Posts: 351
Likes: 0
You can ohm them through the valve cover gasket. Anything more than 3 ohms it is getting weak and will not get hot...right away.
Are you starting the engine immediately after the Wait to Start (WTS) light goes out? The WTS light will go out after 10 seconds or so but the GP's are still activated...for up to 2 minutes depending on the ambient temperature.
Your next cold start, try waiting for 30-60 seconds before starting it. If the idle is better then you have a couple weak GP's.
Are you starting the engine immediately after the Wait to Start (WTS) light goes out? The WTS light will go out after 10 seconds or so but the GP's are still activated...for up to 2 minutes depending on the ambient temperature.
Your next cold start, try waiting for 30-60 seconds before starting it. If the idle is better then you have a couple weak GP's.
Posting Guru
Joined: Feb 2008
Posts: 1,354
Likes: 0
so my ques is my truck had trouble starting in 20 degree temps without being plugged in. if i were to replace all gp's and gpr should it start up with no plug in at college? possible - degree temps at night. im gonna be in the PA mountains
PREMIUM SPONSOR
Joined: Sep 2003
Posts: 2,630
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From: North East Ohio
You DON'T cycle these glow plugs.
Once you turn the key on, just sit there for 60 seconds or so (as mentioned up to 2 min.) then try to start the truck and see what it does.
Waiting for the Light to go off then try to start, then turn off key, turn on key, wait for light to go off, try to start, etc will get you no where.
DON'T cylce the glow plugs, they don't work like that...
Once you turn the key on, just sit there for 60 seconds or so (as mentioned up to 2 min.) then try to start the truck and see what it does.
Waiting for the Light to go off then try to start, then turn off key, turn on key, wait for light to go off, try to start, etc will get you no where.
DON'T cylce the glow plugs, they don't work like that...
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Post Fiend
Joined: Oct 2003
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From: MICHIGAN
It depends on the meter you're using. The lower numbers on the ohm scale gets you the lowest, most accurate readings. Most meters have choices from 200 ohms to 20K ohms to 20M ohms.
IIRC, K means thousands, M means millions
You want to use 200 in this case. It will read from 0 to 200 ohms.
If you use the higher ohm settings (K or M) the needle will just barely move and will be almost impossible to see on analog meters and wou will get an 'error' reading on digital meters.
IIRC, K means thousands, M means millions
You want to use 200 in this case. It will read from 0 to 200 ohms.
If you use the higher ohm settings (K or M) the needle will just barely move and will be almost impossible to see on analog meters and wou will get an 'error' reading on digital meters.