On a 1991 engine does any know what the coolant flow is for the heater and exchanger?
In the thermostat housing there is a ¾” plug next to the lifting bracket and heater hose. I believe this is the return to the block.
Where is a good place to tap into the pressure side of the system, on the feed for the heater core or the feed for the exchanger?
And return it to the top of the thermostat housing?
Reason is I am going to install my coolant bypass filter as my next project.

Also for an electrical question, my fuel gauge has a problem with wandering, sometimes it will drop all the way to empty and then it will suddenly be back on full again. I am sure it is not real accurate and I need to fix it. I do not think it is the wiring under the dash because all the other gauges seem to be ok. Have there ever been any problems with the actual sender in the tank? Like any old TSB’s’
I seem to remember hearing of a problem with the pivot on the float or something. I have a bad feeling I am going to have to drop my tank
I guess what I really need is does anyone have a wiring diagram for the dash wiring or know what and where the color of the wire is for the fuel level circuit. That way I could check the circuit and verify the gauge end is working. Anyone know how many ohms the fuel sender is, that way I can install a wirewound rheostat and simulate the float to check it.
How hard is it to remove the feed and return lines on the top of the tank before you drop it?
Thanks for the help. Jim

 

On the coolant: tee into the heater or heat exchanger feed to feed the bypass, and plumb the return in down by where the lower rad hose meets the block. Those ports there are the low pressure side. If you return it up by the thermostat it won't work very well except when the engine is cold.

My guess on the fuel gauge is a flaky connection. On fuel gauge senders, short to ground = full, open circuit = empty.

I think they changed a lot of the dash wiring between '91 and '93, I'll wait to see if anybody with an older FSM chimes in before I tell you any misleading colors.

 

Don't know if it'll be neccesary for you or not, but the tank's not that hard to drop. You probably don't have access to one, but a motorcycle or ATV jack makes it a BREEZE. You've got a bit of movement before the lines start to get tight so you should have no problem dropping it enough to get inbetween there to disconnect them. Or if you have an engine hoist you can just unbolt the bed with 8bolts + yer taillights being disconnected.

A quick way to find out which wire goes to the guage is to remove the cluster and trace the circuit from the guage to the connector, and from there you can figure out which wire goes to that pin. It's all external on a board on the back of the cluster, easy to see. If I recall though it's the orange wire going into the round connector on the back of the board. Double check that though, I'm not 100% certain.

 

Leece Neville 555 Alternator, now where in the world did you get THAT thing from? That's some serious stuff there. I like it!

 

fuel gauge info...
darkblue, yellow trace
empty >96.5ohms, empty graduation 90 +/- 3, half 45.3 +/- 3, full graduation 12 +/- 3, full <8

 

Thanks for the kind words.
I got it from my heavy truck parts supplier, that was one of the best upgrades I have made to the electrical system next being the relay controls for the headlights.
All of the charging circuit is made using #2 welding cable from the alternator to the distribution block that connects to the battery isolators through a 200 amp T fuse, and I made a #2 ground from the alternator to the block to the chassis. I have not had any low battery issues since.
I can leave my headlights on all day and never have a worry about starting my engine, or my 3000 watt inverter on battery #3
Jim

 

Thanks all of you for the information, I thought it was somewhere around 90 ohms on the sender. I have a feeling it is a bad sending unit but I need to diagnose it a bit deeper, is there any kind of a baffle in these tanks to stabilize the fuel?
When I had the truck in the body shop for painting, they had the bed off for 2 days and he called me and said I could come work on it then but I did not have the time, it would of been so easy then. Oh well that is the way my life usually goes.
On the wire colors, does it follow through to the sender with the same color? And is the wire in the main harness that goes through the firewall or is it under the carpet?
Thanks again.

 

Nope. Not in mine. Which kindof surprised me. As many trails as I've been on I've never had it choke going up or down steep hills. I guess I always have a full tank, so that may be why.

 

its stays the same color. it goes to a blue harness (left side under insturment panel) then it goes to a 5 pin harness i assume is on the top of the tank..

 

Thanks guys, I will try to check it this weekend if the ground cools off enough to get under the truck.

Can you believe the price of fuel in the last week? It's now $3.49/ gallon when last week I paid $3.05/ gallon.
So much for them helping us out in a crisis.
To get to the I10 freeway, I have to drive about 3 miles south. There are 4 gas stations
Shell-$3.59, Valero-$3.39, Arco-$3.49 and 76-$3.49
Last week I had to go into the valley and the price right off the freeway {Topanga Canyon Blvd.} was $3.89/ gallon but as I drove about 3 miles the prices at the same brand stations were down by $0.50/ gallon. Guess the ones by the freeway had a higher gouging margin and less of a conscience.
Jim

 

I guess I won't cry to you about $2.89.

 

i remember complaining when it hit 2.40, irony sucks... highest ive seen is 3.70 in newport and lowest 3.40, id been on my low fuel light for a while so i put 5 gals in to get home and ill try to wait it out... but it really doesnt matter because the gas consumers are happy and thats all that matters, just dont explain to them the more diesel goes up the more everything else will.