Let me start by saying I used the search function here but could not find a situation like mine.

Here are the truck specs:
1988 F-150
2 Wheel Drive
351 Engine
68,700 miles
Dual Fuel Tanks
I've had the truck for about 8 months and have never had this issue before.
It was colder than anytime in my ownership when this happened.

Here's the story:
I was taking the truck on a 20 mile drive to the airport to catch a flight.
I was running on the rear gas tank.
The rear tank gas gauge read below 1/4 so I switched to the front tank mid-ride.
After about 10 minutes on the front tank, the truck sputtered and the engine shut off.
While moving I switched back to the rear tank, restarted the truck and continued to a gas station and filled the rear tank.
I went on my trip.
The truck then sat for 5 days at the airport.
Upon my return, I went to start it and it would crank but not start.
Towed it to my mechanic who has not had time to look at it yet.
Today I went there to tinker with the truck.
Crank, no start.
I put some fuel down the vacume line for the power brakes.
Started right up and ran great.
I ran it for well over an hour.
During that run time (no driving just sitting in the parking lot) I did the following:
Switched between the front and rear tanks many times with no change in idle.
Ran the truck at various RPMs again switching between the front and rear tanks with no change in the engine performance.

I'm making the following assumptions, please correct me if I'm wrong:
The fuel pumps in the tanks are working.
The switch to go from the front to rear tank is working.
The Dual Function Reservoir Valve is working.

What should I do next??
I left the truck at my mechanics.
We are going to let it sit for a few days and try to start it.
I can't afford to start throwing parts at it, so I want to be smart here.

Thanks in advance.
Tony

 

Even if the check engine light isn't on, the computer may have logged some codes that can help pinpoint the source of your problem. Have the codes checked if you don't know how, that might get you going in the right direction.

 

I bought an OBD1 Code Reader.
I performed the test with the Engine Off / Ignition On to get the continuous memory reading ("C")

Here's what I got in the order I got them:

14 = Ignition Profile Pickup (PIP) Circuit Failure
18 = Loss of Tachometer Input / IDM Circuit Failure / SPOUT Circuit Grounded
32 = EGR Pressure Feedback Fault

Should I replace the coil pac, wires, cap plugs etc..??
Any other thoughts?

 

Could be circuitry problems, likely your ICM is going out. There is an electronic pickup sensor mounted inside the distributor that gives off a signal the PCM uses for timing, that may be the problem as well. I had a problem with loss of input, ended up being a bad resistor in the engine wire harness.

 

Update:
Just for $h1t$, I cleaned the contacts on the coil pac wire that goes to the distributor (both ends) and reinstalled the wire.
The truck started better than it ever started before.
I took it for a ride and it had at least 40% more power than before any of this happened.
Frankly, I thought the prior power was standard for a 1980's truck.
Since all my important codes seem to be electrical related, does this make sense??
I was thinking about clearing the codes and seeing what happens.
Thoughts?

 

Tonight I went out to erase the codes as described in my last post.
Before erasing, I decided to check the codes again.
There were none there.
Not even in the continuous memory, which I understood was to hold all historical codes.
I'm confused.
Can someone please chime in.
FWIW: I'm fairly competent with non-computered old cars.
This electronic crap has me at loss.

 

Maybe you accidentally cleared the codes, see reader manual page on clearing codes.

 

Did you run the KOEO & KOER again ?

 

I ran the KOEO Key On Engine Off
Fairly sure I did not reset, but??

 

So, i'm not clear, did you at the least get pass codes ? ""8"cyl" ? Square block flashing?

or, Tests ran but no codes displayed ?

or, Tests did not run ?

 

Yes all the proper flashing took place on the OBD tool.
Tests did run.
The code 14 and 18 no longer showed in historical memory.
I'm fairly sure I did not erase them.
The are no codes coming up at all.
I'm going to take it for a long ride tomorrow (not far from home as I still don't trust it.) then run the code test again.
Since all my codes before seemed to be electrical (not fuel) I'm wondering if cleaning all the contacts did the trick.

 

I just took it for long enough of a run to get it to full operating temperature.
Started right up no problem.
Made good power.
I only noticed a very, very slight hesitation at idle.
When I got home I ran the codes; Key On Engine Off.
Now, the only fault that came up was #32 which is EGR Pressure Feedback Fault.
Nothing else.

 

Well, it looks like your EECM is capable of generating codes…..

A Code #14 may cause a Code #18. Cleaning the SpOut connector can solve a Code #18.
A Code #14 can be erratic as the ICM/TFI can be intermittent.

You can check for the PIP signal when it is not starting.

"Da_Lariat_Chariot ;
Could be circuitry problems, likely your ICM is going out. "

Like he said.


Engines are easier to diagnose over the internet when all the codes are listed, and in order of test.

KOEO - (O) Self-Test Codes =
KOEO - (C) Continuous Codes =
KOER - (R) Self-Test Codes =

Make sure your A/C, Heat, Radio, etc. are turned off when testing.
The "10" appears during KOEO to indicate the start of Continuous Memory Codes.
The "10" appears during KOER to indicate the start of the WOT test.

 

As of right now this is it:

KOEO - (O) Self-Test Codes = 32
KOEO - (C) Continuous Codes = 32
KOER - (R) Self-Test Codes = I'll do it tomorrow

 

If anyone is interested......

I did the following:
1) Cleared all the codes
2) New plugs, wires, cap & rotor
3) Cleaned a bunch of electrical connections
BTW: Old plugs were a nice golden color...perfect.
4) Noticed that the famed "Pink Plastic Vacuum Line" was broken in it's conduit.

Drove the truck to get it to full operating temperature.
BTW: It made great power. Better than ever before.

I ran the codes:
KOEO - (O) Self-Test Codes = 32
KOEO - (C) Continuous Codes = 32
KOER - (R) Self-Test Codes = 44 & 32

So my game plan is to remove and replace all the hard plastic colored vacuum lines with silicone colored vacuum lines and see what happens.

Will advise.