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Discussion Starter #1
I had the injection pump and injectors replaced recently. Fuel mileage prior to replacement was 19-21 mpg. Now it is @ 16 mpg. I do spend more time driving at 65 mph on the freeway, but 16 mpg seems low.

Do rebuilt IP's come factory set? Is there a "break in" period for the pump? Should the timing be reset?

Thanks in advance!

Larry
1982 Chevy 1/2 ton P/U
200K miles (great truck!)
 

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Are you getting any more or less smoke than before?

Black smoke?

Fuel mileage is possibly due to the timing of the pump on the engine. Where are the timing marks on the front timing cover as compared to the mark on the injection pump itself?

And finally, sometimes when tinkering with the pump, the lockup switch for TH700 tranny gets moved and you'll not get the lockup of the torque convertor, so you'll loose MPG, but I wouldn't think the amount you're seeing.
 

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Does your truck feel like it has more power?

The reason I ask is my 82 diesel gets 20-21mpg with a 3 speed and a fairly low gearing but it has very little get up and go at least compared to my 89 6.2 suburban. It seems that the old IPs were "underpowered" but seemed to give good mileage even when combined with unfavorable gear ratios. Not really sure why.

Good Luck
 

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Discussion Starter #5
I just had the 700R4 transmission rebuilt. There was no power to the lockup, so I'm sure that affected the fuel mileage. I'll check the mileage again.

Larry
 

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Yep, if the lockup wasn't working, that would drop your fuel economy drastically...
 

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Most pump shops set the pump to the "high side of specs". According to them, they get more complaints from lack of power than from low fuel mileage. If the pump is set to give the best fuel economy, power will generally be down somewhat. It's a natural tradeoff. My shop calls it "Ten Percenting" the pump. Something about increasing fuel by ten percent from the original settings. Part of this original number is due to DEQ (emissions) and CAFE requirements.
 
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