When I bought my truck, the owner said that he had some cold temperature start problems. One day while I was admiring my sweetheart I noticed a blown fusible link near the missing water separator. Replaced the Separator (thanks Bricklayer) and noticed that a wire was pinched under my valve cover gasket and it appears to go to a vessel near the fuel filter. Replaced the gasket and moved the pinched/ shorted wire, and installed a fused link, no short. I saw in a manual that the truck has a fuel heater. Does anyone have a schematic of this relay circuit and at what temperature does it operate and/ or cycle? How does it work? I have the feeling that this may have contributed to the cold start problem since the previous fuel/ air leaks have been repaired and she starts rather well in mild temperatures. So I'd like to get this fixed or test it before the cold weather strikes. Also, the manual says that it is equipped with a block heater- something I knoticed was removed and plugged, should I install one? It seems easy once I remove the starter- appears to be plenty of room to install?Thanks in advance all who reply.

 

86 wiring can be found here... http://community.webshots.com/album/202816966sObdCc

as far as operation the heater is located on the lift pump to fuel inlet line to the filter header and comes on at 32*F controlled by an internal thermostat.

Check you engine serial number and ensure it is an 86 block....

According to the update I have the updated casting was implemented starting with block number 173828 (which translates to roughly halfway through the '85 model year).


6.9 blocks up to serial #u2u17900 had a thinner casting around the block heater. It is very common for these blocks to crack.

6.9L Old Style Block

Block Casting Number:


On left side of block (beneath oil cooler) 1805440C1
Note: Some 440 blocks are truly new style and must be visually inspected by raised donut around the block heater, frost plug (right rear). Old style below serial number 173828.
Visual Identification: *No counter bored area for block heater
*No defined area on side of block for dip stick
*Thickness of cast iron around block heater 3/8" (.375")
Head Bolts: *7/16, 12 point socket is used to torque head bolts
*Block tapped with 7/16-14 for head bolts

6.9L New Style Block

Block Casting Number: 1807996C1 Note: Some new style blocks have casting
number 440. Above serial number 173828.
Visual Identification: *Has counterbored area for block heater
*Very defined relief area cast in side of block for dip stick tube.
*Thickness of cast iron around block heater 15/32" (.470")
*Latest style (not all new style 6.9) has ribs around head bolts, rear two on left side go from head gasket surface to pan rail - same as 7.3
Head Bolts: *Same as old style 6.9

 

Sounds like alot of information and my brain is swimming. I dont have the #'s but my block does have an indent for the oil dip stick, and there was a universal rubber plug at what looks like a freeze plug location. BUT I don't remember if that "freeze plug hole" was raised or not. I'll have to check. I dont remember seeing an oil cooler either. And, the previous owner said that he had to tighten the oil filter like He** to keep it from leaking, so Im not looking forward to removing it. Thanks.

 

The voltage for the fuel heater is in the same circuit as the injection pump sol. ect. It is a hot on run and crank.