Hi all
I have a 1988 Econoline E150 which runs on LPG but will not run on gasoline, I am starting to look at the problem as it has never run on gasoline since I brought it and was like that for the previous owner. I have started fault finding but wondered if I can pick your brains as have found a few things but it still does not start.

Firstly tested the dual tank changeover switch as follows:-

Checked Pin 2 of the switch for presence of 10 to 12v when engine cranking, test revealed this was NOT present!!.

Removed changeover switch from electrical connector and tested switch itself.

Ensured "FRONT" tank selected via switch:-
Checked for continuity between Pins 1 & 2 - OK!
Checked for continuity between Pins 4 & 5 - OK!
Checked Pins 3 & 2 were open - OK!
Checked Pins 6 & 5 were open - ok!

Ensured "REAR" tank selected via switch
Checked for continuity between Pins 3 & 2 - OK!
Checked for continuity between Pins 6 & 5 - OK!
Checked Pins 1 & 2 were open - OK!
Checked Pins 4 & 5 were open - OK!

So testing revealed switch was not physically at fault but it was missing the 10 - 12v supply!

Looking at a wiring diagram noted the power from the Fuel Pump relay went through the inertia switch to get to Pin 2. So took a look at the inertia switch with a view to doing some testing for the missing voltage.
We found the terminal on the inertia switch was melted and was in a terrible state - see pics below:-



There was continuity from the pink wire on the inertia switch to pin 2 on the tank selector switch, checked the other wire which was orange/ blue and this had 10 - 12v on it so thought great found the missing voltage. So we cut the connector and wired the two wires together to effectively bypass the inertia switch, also the inertia switch rattles inside badly (is this normal?????) and the terminals are also badly burnt.

So backtracked up to the green 4 pin Fuel Pump relay under the hood, it had pins numbered 1 to 4 and I found these to be:-
Pin 1 = Tan wire / Green stripe - Fuel Pump Relay control
Pin 2 = Red wire - Power from EEC Power relay
Pin 3 = Should be Brown Wire but orange / blue on mine - Fuel pump outlet
Pin 4 Yellow wire Ignition fused power (fuel pump fuse)

Everything there seemed to be functioning correctly voltage wise. So went back to pin 2 on the tank selector switch as after wiring the inertia wires together I should now have 10 -12v at pin 2 then - I do for an instant then the power just disappears to 0.00V???? Any ideas?

I am suspecting the green relay may be at fault, but as it is labelled just terminals 1 , 2 ,3 & 4 I am unfamiliar with how to test this type of relay as all the ones over here in the UK use the ISO number of 30, 85,85a etc.
Anyone know how to test this relay and whether it sounds from all the testing that you would agree the relay may be the culprit?


Also when I turned the ignition on and got the momentqary 12v would this be the circuit priming the fuel pumps?
I need to get a friend to help me check if a noise can be heard, are the furl pumps inside each tank, also have no voltage at the high pressure fuel pump, should this also prime?
Welcome your thoughts!
Thanks
Mark

 

Unfortunately I can't help with the numbering of the relays since I'm only used to the 30,85,85a as well. to answer your question in your last paragraph though, yes the momentary voltage is to prime the fuel system, to keep the fuel pressure up for the injectors, which I'm assuming you probably have the TBI style on yours. You should also get the voltage at the high-pressure pump (if you have one) to prime the fuel pressure.

 

Hi Leon
Thanks for the info I will investigate in more depth now why I don't have the voltage at the high pressure pump, will also check if I can hear the fuel pumps priming as stupidly was listening to the high pressure pump!
Thanks again
mark

 

Quick update - Found break in wire to high pressure pump and now have the momentary voltage there, next job is to drop middle tank and check wiring from tank back to switch for continuity, will also put a resistor across the terinals to see if I can get the fuel gauge to move as still inactive.

 

Quick update


Pegged fuel gauge at the duel tank selector switch (ie grounded the wire to fuel gauge) and the needle moved from 'Empty to Full, so the gauge in the instrument cluster is definitely working!


Managed to find a connector plug near to the rear tank and disconnected it, it had 4 wires going to the plug - 2 x earths and 1 x Fuel pump and 1 x sender unit wire.
Checked continuity of the wires from the selector switch to both the fuel pump and sender unit wires at this point and they were fine!


Checked the two earths to ground at front of vehicle where I had been testing - nothing! Ran a wire from the negative post of the battery and replaced the two earths, tried priming the rear pump - nothing!. Pegged the fuel gauge from the rear of the van at this point and gauge went from 'Empty to Full', so next stage is to drop tank, check remaining section of wiring and check unit inside tank - so we're making some good progress.
Also took the opportunity to check the van for any fault codes using the check engine light flashing method and got one fault code 63 - TPS (Throttle position sensor) voltage low / less than 0.6 volts. I have parked this code at present until we have the tank out and can see what is going on but the TPS fault could be shutting off the injectors, but firstly I need to know if I am getting fuel out the rear tank and up to the front. I don't have a fuel pressure tester and have asked around without success so once the tank has been out I may have to try a garage I know for a quick pressure test at the shroder valve.


So all in all good progress made but haven't sorted the fault as yet but we are definitely closing in!

 

You won't need a gauge to check fuel pressure at the rail, if fuel comes spraying out when you depress the pin on the schrader valve then you have fuel pressure, it's kind of a on or off thing, checking the pressure with guage would be needed to diagnose a driveability problem but not so much for a no start condition..
The Inertia swith is there to shut off fuel in event of collision so you can work around it if needed..


Different application but 4 pin relays should be similar in function, view the switch so the terminals are properly oriented..

Pin 86 goes to pump
Pin 87 goes to Inertia Switch or Fuel tank selector in your case
Pin 85 is ground
Pin 30 is battery +

 

Hi


Thanks for the info on he fuel rail much appreciated, didn't realise you could do a simple 'fuel there or not test', this is just what I need. Will check and report back with results.


Regarding the inertia switch I have wired this out for the time being and simply joined the two wires going to it together after checking wiring diagram, will get a new switch in the future once van running on petrol again.