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Junior Member
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56 Posts
Discussion Starter #1
hey all of a sudden my truck went from getting about 16 to 18 mpg to like 5.. it seemed to drop once the temps started to drop.. any ideas as to why this would happen? also if i am running a push button switch for my glows how long is the limit for them to be on? im getting ready to put some zd9's in it. thanks
 

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TDG MAFIA
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730 Posts
Are you sure you are calculating your MPG correctly? 5PMg ive never heard of something that low. Are any of your brakes dragging, you Emergency brake on? Glowplugs wouldnt cause any issues with MPG. For your push button question, 10 seconds is what you will want to hold them on.
 

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Gone Fishin...
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3,099 Posts
Winter fuel will cause a drop in fuel economy, but not by that much. Not to sound like a smart ***, but is the truck leaking fuel?
 

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Super Moderator
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4,247 Posts
At 5 MPG the smoke trail from the tailpipe, fuel in the oil or coolant or leaking onto the ground would be the things I look for.

How long to push the GP button depends on which GPs you have:

Spade (older) type GPs = 10 - 15 sec cold.

Bullet (newer "fast start") type GPs = NO MORE than 10s or you WILL fry them.

That assumes you have OEM "BERU", Motorcraft/International GPs, if you have aftermarket ones, well pray.
 

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Senior Member
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4,827 Posts
Low power? Hard start? White or excessive black smoke? More engine rattle?

Possible causes-

Dragging brakes (even caused by worn ball joints)

Bad air filter

Low fuel pressure

retarded timing

air leaks in fuel system

fuel leak

That assumes you have OEM "BERU", Motorcraft/International GPs, if you have aftermarket ones, well pray.
Well put. LOL
 

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Junior Member
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3,533 Posts
You also want to check the muffler, if a baffle breaks loose it will back up and block flow. Usually it will sound different, and when you put your hand over the tail pipe it will have an even flow and possibly even whistle.
 

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Senior Member
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4,827 Posts
:whs

Boss blew his headgaskets out on his 5.7L Vortec when the cat took a dump. Plugged that pig right up. LOL
 

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Junior Member
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56 Posts
Discussion Starter #8
thanks for the info, no its not leaking any fuel and i haven't noticed any fuel in the oil or coolant... im thinking that the e brake cables are bad and not letting it release the whole way... seems like it really sucks down the fuel on the highway not so much around town... gonna save some money and replace the brake cables asap.
 
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