1990 F150 in sig. Decided to change out the float in the front tank yesterday. Picked one up at the junkyard, tested it, no holes, and started to install. Dropped the front tank, disconnected the two fuel lines, the filler tube, and another line with its own separate circular plug. (What is that?)

Removed the sending unit, replaced the float. Old one was full of gas. Tested the gauge by manually moving the arm with the new float. Worked great. Ready to reinstall. Reinstalled sending unit, lock ring, fuel lines, line with circular plug and the filler tube. Everything strapped in. Put in 2-3 gallons of fresh fuel in the front tank. Turned on the key, switched to the front tank and the measurement was good. Above empty, but not a lot.

Decided to go ahead and try and start the truck on the fresh fuel. Would not start. Ok, let's try the back tank. No start. Battery is not drained, it's getting late and I'm tired. Stopped for the evening. Went out after church this afternoon and pulled the following codes.

15 - failure in electronic control assembly ECA. Problems with keep alive memory. I suspect this is caused by the low battery.
21 - Engine coolant temperature sensor signal voltage: out of range (Key On Engine off self test), not at normal operating temperature (Engine run self test) or loss of signal (during normal engine operation) or Electronic Distributorless Ignition System (EDIS) fault - problems with crankshaft position sensor CPS circuit
24 Air Charge temperature ACT sensor or vane air temperature VAT sensor-siginal voltage is out of specification (engine off) or not at normal levels (Engine Running)
67 - Improper signals are being received from either the neural drive switch, neutal gear switch, neutral pressure switch, clutch switch, Manual Level position snsor or air conditioner clutch.

I checked all of the fuses inside the cab. All fine.

Truck will crank, but not start. have not tried spraying starting fluid into intake.

Suggestions?

Much appreciated.

Hunt4fun

 

I forgot to include that fuel pressure at the rail is 32 with the key on. When trying to start, the pressure does not change.

 

Those codes are all normal for a battery disconnect, cold engine, cold outside and you did not push the clutch down.

32 PSI is to low to start a 4.9L engine.

Sounds like you have fuel system electrical problem now.

 

Ok. Sounds reasonable. I thought it would be fuel related but the 32 psi was throwing me off.

I'll start with the electrical connector on the front tank.

Could it be that I'm not getting enough pressure because of some kind of leak? I'm still wondering what the separate tube with the round connector is. I wonder if it is not making a good enough seal and therefore I'm loosing pressure. I'll check a few items and change the fuel filter as well.

Thanks for heading me in the right direction.

Hunt4Fun

 

I would not think so unless it was inside both tanks.

It is the vapor valve assembly for the Evaporative Emission System.
Fuel vapors trapped in the sealed fuel tank are vented through the orificed vapor valve assembly in the top of the tank. The vapors leave the valve assembly through a single vapor line and continue to the carbon canister (located in the engine compartment or along the frame rail) for storage until they are purged to the engine for burning.

 

I have to wonder if the fuel ines got crossed at the pump during re-install. It's most like something common to both tanks. The truck is a '90 so the transfer valve, is electric (if I'm not mistaken), there's no third fuel pump as the both in tank pumps are high pressure. Pressure regulator perhaps?

Not much help, sorry.

Tim

 

No transfer valve on the 1990 F-150.
The fuel lines are two different sizes (pressure and return) so you can not mix them up.

 

I'm going to test the pressure from both tanks at the rail. Since it won't start with either tank, I expect it will be the same. I'll also change out the fuel filter in case it is clogged. And I'll check the lines between the filter and the rail.

Hunt4Fun

 

Make sure you ground pin #6 of the EEC test connector with the key on or the pressure test will not mean much.



/

 

OK. I didn't do that when I got the 32 psi reading. I'll find that out this evening. So does that mean that my 32 psi reading is incorrect?

As always, thanks!

 

Did the testing this evening. No pressure from either tank with the EEC test connector grounded. Removed the fuel filter. Ran a test on both tanks and the pumps work fine. It got dark on me so I couldn't do any more testing. I have a new fuel filter and will install that tomorrow. I may also verify that the line from the rail to the filter is not clogged.

 

Look for a pinched fuel line also.

 

That would certainly explain it.

Good idea. I'll check for that as well,

 

As usual, subford was right.

3 kinks in the line. Probably explains why it would die or nearly die when coming to a quick stop.

Off to the junkyard tomorrow. Advance, O'Reilly, and AutoZone did not have the part. I need the line from the fuel filter up to the engine.

Thanks again, Bill.

Hunt4Fun

 

The fuel line has been repaired. All of the kinks have been removed. Fuel Pressure is now at 34 psi. I changed out the battery in case it wasn't giving the fuel pumps enough voltage to come up to 50 or so. No change.

I'm somewhat at a loss on where to go from here to diagnose the problem. Fuel Pressure Regulator?