wiring diagrams and other service info

[jim x 3]

List:

"I am troubleshooting a dual fuel tank switchover/gauge sender problem.

I have checked the Autozone web page(s). They show 31 diagrams for the 1987-95 F-series pickups (same as the Chilton diagrams I've seen) and NOT ONE diagram shows a fuel tank sender or gauge (or the dual tank switchover switch or actuator for that matter).

Maybe I'm spoiled since I've never owned a Ford before, but how do you guys manage with such sucky service info?"

Further, Helm has no offerings for this truck model and year.

The local Ford dealer parts guys just laughed when I asked at the parts counter for wiring diagrams and other service docs.

None of you guys, except chuckster and maybe cdn seem to have any info.

I guess I can contact the manufacturer and ask how they expect to keep these trucks on the road if documentation isn't available.

Anybody know what a service manual for an '88 F-350 would go for on ebay? If they're available I bet they'd be costly.

I'm not happy.

Regards,

[ARIZHNT]

What kind of problem are you having?

There are a few common failures with the fuel system.

[jim x 3]

AZ,

Thanks for asking. I'm really looking for some background info so I can solve other problems in the future as well. Thus my rant about service info and diagrams.

Right now, the fuel tank problem(s) symptoms are:

* Gauge reads well over full when tank is just full
* Gauge declines as fuel is used, but swings wildly, particularly at certain fuel levels
* Sometimes gauge drops very quickly to less than empty
* Engine dies at 1/4 tank, particularly when fuel is sloshing
* Both tanks have the same symptoms

I have searched and found a couple of posts referencing a "flapper" on the in-tank fuel pickup. I'd like to verify correct action of the chassis wiring and instrument panel before I start dropping the fuel tanks to check the pickups and sending units.

Thanks,

[Snotzalot]

1/4 tank you have a bad pick up.

[jim x 3]

Hey Snotz, yeah I kinda figured that.

But the fact that the gauge swings around wildly indicates at least one more problem. It could be in the tank sending unit, it could be a short in the chassis wiring, or it could be in the instrument panel.

If I was working this problem on my Toyota, I would look at the service manual p. 17-29 which has a little table that shows the (Toyota) sending unit puts out 3 ohms @ F, 33 ohms @ 1/2 tank, and 100 ohms @ E. So I then attach a 33 ohm resistor to the sense wire (removed from the sender at the top of the tank) and ground the other resistor lead. Then the gauge should read 1/2 tank. If it does and doesn't swing wildly when the truck bounces around, then the problem is in the tank. If it doesn't read 1/2 tank, the problem is in the wiring or instrument panel. If it reads 1/2 tank but swings when the truck bounces, I've got a chassis wiring short. (And I can use the 33 ohm resistor at the gauge in the instrument panel to further isolate the problem if necessary.

BUT WITHOUT THE TABLE IN THE MANUAL I"M SCREWED.

Anyone, how about some help? What are the wire colors and locations, and what is the relationship between tank level and resistance in the sending unit for my Ford?

Regards,

[rsr911]

I found the main library to be an invaluable source, they had professional service manuals for nearly every vehicle you can think of going back 20-30 or more years. I made copies of all the appropriate wiring diagrams. Those diagrams have the color codes for every wire. My are for a van so I doubt they'd be much help to you.

[RWF350]

I am lucky, I have access to AllData at work, but also within days of when I bought my truck in '92 I coughed up the bucks and bought the full set of Helm books for mine. I learned it from my Dad. He bought the full set for his '69 f100 in '69, I bought the set for my '81 f250 with in days of buying it (around '87), the family cars, the tractors (which I even have parts catalogs for),etc. But I know what you mean, I have had to bring my books to work for trucks in our shop before. The techs kind of laugh at how picky I am over them, but even the books for the '69 are almost still perfect.

[NH2112]

We have an '88 light duty F-series FSM at work, I'll see about photocopying & scanning the applicable pages. If you have a fax I could send them that way, too. It's a very handy book to have.

1988 FORD F-150 BRONCO E 250 350 TRUCK SHOP MANUAL 88:eBay Motors (item 380173697305 end time Dec-01-09 13:15:19 PST)

[jim x 3]

Guys,

Thanks for the replies and offers for help - I need 'em all.

I checked the Sacramento and EL Dorado County libraries for manuals first - they each had a Chiltons. I checked it out, but my opinion of that book is shown previously in the thread.

On ebay, it looks like I can buy a 2-vol. manual set for $107 and a diesel engine supplement for $58. This is 15% of my purchase price for the truck itself! And since I've never actually seen the manuals I can't judge their quality and value to me. But I guess stuff that's rare and useful is valuable. I'll have to do without (at least for now) - my service budget needs to be saved for something even more important - like a new GP relay, or ABS module, or coolant, or filters, or tires.

Regards,

[caliph]

Originally Posted by jim x 3

What are the wire colors and locations, and what is the relationship between tank level and resistance in the sending unit for my Ford?

....looks like you've probrably already got this, but i can try to email you this diagram if you still need it.

[jim x 3]

Cal,

Thanks for the offer - I got the fuel system specific diagrams and info from RWF350.

Regards,

[cdnsarguy]

Your problems are:

Fuel pickup(s) broken off at 1/4 full...............

Senders in the tank are worn out........ available at rock auto

Here are the fuel guage test #s

22 ohms sent to the guage it reads empty "E"

145 ohm sent to the guage it reads full "F"

Here are the sender test #s

Sender at empty stop 14-18 ohms

Sender at full stop 154-162 ohms

Check my photo link for pics..................

[jim x 3]

Guys,

I've just made a commitment to this 7.3. I bought a Ford service manual set for the 1988 F series. So I should have everything except the 7.3L diesel supplement.

Thanks for the assistance so far,

[Plywood]

Anyone tried just cutting a hole and installing a marine fuel tank doo dad such as one of these. A different gauge would be needed of course. But the sensor is universal length, or customizable anyway.
FUEL TANK ACCESSORIES

It's one of the things on my mental project list, right now I have no gauge but I made a fuel pick up so I can run down to past 17 gallons for sure, and likely more.

I ended up just removing a tank and the selector valve once I figured out there were six quick disconnects just on the valve.

My valve started sucking from one tank and returning to another. Diesel was coming out the cap, I had had enough.

[ARIZHNT]

Both of my pickup tubes broke off, and the front float leaked on mine. I repaired the pickups with 3/8" fuel line and replaced the front tank float. So far they both work fine now. I spent around $15.00 for everything.