wierd fuel/electrical problem

ok guys, got a good one for ya

saturday morning i went to start my b2. it started then died. tried again, started and died. tried again, this time holding the pedal down a little, as i figure that my iac valve is goin up. i run it for 30sec or so, gently let off the pedal. runs for a couple of seconds then died again. this time it wont start for a few minutes, and i notice that i dont hear the inline high pressure fuel pump running. so i cycle the key for a few minutes, and i finally hear the pump kick in. start the b2 u and off i go.
i get 2 miles down the road before the b2 dies and wont restart. after 10min of cycling the key the pump kicks back in and i get home. i tinker with it for a few minutes, and cant figure out whats wrong. i hit the inertia switch button a few times, figures that hey, it cant hurt anything. voila! it starts! so i take off again and dont even get a mile down the road this time. my dad has to pull my back home.
now im figuring that he high pressure pump is going up, i mean after all, its not running. so i run into town and get a high pressure pump. get back home and take the old one off, which was a real pain in the ass, and get chemical burn down my right arm from the fuel injector cleaner i put in friday night. before i put the new pump on, i get my handy dandy multi-meter out and test voltage to the pump...6.9v! guess its not the pump after all!
i get my chiltons and look at the wiring dragrams, and i learn that power goes from the fuel pump relay to the inertia switch to the high pressure pump to the low pressure pump in the tank. i also notice that the same wire that goes to the switch splits somewhere and also goes to the ecm(why??) im gettin 6.9v at the inertia switch, but 12 out of the relay. next i test continuity between the relay the and switch, and cant find any(though, it just occured to me that i probably had the key on while trying to find continuity, and i wonder if u can find continuity in wires that have voltage going through them, due to the interference with the signal voltage from the meter...?).
now im wondering if im testing the rights wires, so i look at my diagram again...yup, testin the rights wires. orange/light green out of the relay to pink/light green to the switch to red/black from the switch. at this point im thinking a wiring problem cause excessive resistance, but just in case im missing something i test my ex auto tech teacher(god love him, he's helped me out on my fords so many times). he tells me that the ecm sends power to the pumps for only 2 seconds before cutting the power off if the engine isnt running...interesting(because im getting a constant 6.9v).
eventually i try to start the b2 and it starts up, yay(i had beet on the panel above the ecm a few times, though im not sure if this did anything)! i notice that when the b2 works correctly, i do in fact get the 12v power for 2 seconds, then it cuts off. now, i also get continuity between the wires. but i notice that out of the relay on the orange/light green wire im still getting 12v when the power to the pumps is supposed to be off, but no power to the switch...interesting again. i deduce that there must be something else between the relay and the switch that the ecm controls to cut power off to the switch...but this makes no sense, as the ecm controls the fuel pump relay in the first place(what again, whats the deal with the orange/light green wire splitting and going to the ecm??)
at this point im thinking a wiring problem in the orange/light green wire at the split where it goes to the relay and the ecm...but i dont know where the split is. or im also thinking an ecm...but really im stumped.
the b2 started starting up again sat night, and started all day sunday, and it started today, no problems. all did was mess with the plugs from the inertia switch to the relay. but even if it was a plug it wouldn't have cause that constant 6.9v, so in reality i did nothing to fix the problem, the problem just went away. i did some digging into the wiring harness where the relays are and couldn't find the split in the orange/light green wire...maybe i just didnt go deep enough, i hate old electrical tape thats all sticky.

thoughts, ideas, suggestins? help!

is there another relay in between the fuel pump relay and the inertia switch thats not on the diagrams? where is the split in the orange/light green wire? what would cause the constant 6.9v(ie where is the constant 6.9 coming from, as most hot wires are 12v)? anyone think that its the ecm back feeding power into the split ?

also, when i say constant 6.9v, i mean constant, there is no variation. i read 6.8v once, but i was messin with the probe. i say this because if it was a short between 2 wires(1 constant hot and the orange/light green wire) then i would expect the voltage to variate a little as the wires move or pressure changes. hell, put a multimeter on a battery and unless u hold the probs at the same pressure and very very still the voltage variates on the meter!

First, replace the relay. 6.9v at the inertia switch almost has to be a bad relay.
Might also replace the ECM relay, since IT probably controls the FP relay coil.

Next, I'd either replace or jumper out the Inertia Switch. To jumper it, simply remove the connector and put a solid wire in the two pins and tape them so they can't short to anything. I say this because I can't tell from your description whether you are getting 6.9v coming out of the Inertia switch or to the Inertia switch. Its connector could be corroded.

I'd also look for and clean the grounds. Try the one(s) on the DS and PS fenderwells, make them bright. Might as well hit the one on the radiator support and firewall to engine too. Can't hurt.

Earl43P said:

First, replace the relay. 6.9v at the inertia switch almost has to be a bad relay.
Might also replace the ECM relay, since IT probably controls the FP relay coil.

Next, I'd either replace or jumper out the Inertia Switch. To jumper it, simply remove the connector and put a solid wire in the two pins and tape them so they can't short to anything. I say this because I can't tell from your description whether you are getting 6.9v coming out of the Inertia switch or to the Inertia switch. Its connector could be corroded.

I'd also look for and clean the grounds. Try the one(s) on the DS and PS fenderwells, make them bright. Might as well hit the one on the radiator support and firewall to engine too. Can't hurt.

Click to expand...

im getting 6.9v to and from the inertia switch, but 12v out of the relay(when it wont run). the FP relay wouldn't cause this, simply because the problem is after the relay.
when it acts correctly im getting 12v out of the relay and nothing to the inertia switch(with engine not running, key on, after the 2 second power up) which is what is supposed to happen. im just not sure what comes after the relay and before the switch to cut the power out
no corosion on the inertia switch connector, i checked.
good idea about the grounds though, i will try that.

Is there any chance that you can summarize the issue?

What year of B2 do you have? Edit, n/m, missed it. I have the EVTM for an '88.

You might look into how to test the fuel pump circuit from the diagnostic connector. I know it can be done, but never had to do it personally. Something tells me it could just be a matter of grounding one of the connections, but I would definitely reference a diagram for insurance.

Pete

Psychopete said:

Is there any chance that you can summarize the issue?

What year of B2 do you have? Edit, n/m, missed it. I have the EVTM for an '88.

You might look into how to test the fuel pump circuit from the diagnostic connector. I know it can be done, but never had to do it personally. Something tells me it could just be a matter of grounding one of the connections, but I would definitely reference a diagram for insurance.

Pete

Click to expand...

i did that. as far as i could tell all that really told me was whether or not the pumps had the correct voltage, which i could find out just by my multimeter or starting the engine.

summary:
my b2 intermittently stalls out or wont start due to incorrect voltage to the pumps. when stalled/no start i have a constant 6.9v with the engine not running
the 6.9v is before and after the inertia switch, but im getting 12v out of the relay. at first i could not find continuity between the relay and the switch, but now i can. wiring diagrams say that the wire out of the relay splits somewhere and goes to the ecm and the switch.
when operating correctly i have 12v for the first 2 seconds of key on engine off(which is whats supposed to happen)
when operating correctly, after the first 2 seconds, i have no power before/after the inertia switch(correct) but 12v still coming out of the fuel pump relay
im deducing that there is another relay controlled by the ecm after the fuel pump relay but before the inertia switch and is simply not on the wiring diagrams -or- maybe the wire out of the relay goes directly out of the fuel pump relay to the ecm then to the inertia switch, but then why have a fuel pump relay in the first place?
furthermore i am guessing that my problem is somewhere in the wiring or an ecm but cant confirm.


still a long summary, sorry.
oh, and after i beet on the panel above the ecm and messed with the wires and plugs around the relays it started starting again but i think thats just coincidence

recheck the grounds
there should also be a ground for the ecm on the door post.

Are you taking these voltage readings with the inertia switch and both pumps connected? If so, it's time to suspect the lift pump in the tank. It could be bad, dragging down your 12v AND not delivering fuel to the HP pump.

Perhaps you could convince Psychopete to send you the pages out of the EVTM?

the drag on the low pressure pump is a good idea. but one of the things i did when testing the voltage was unplug the inertia switch and checked power at the plug...still 6.9v

hey physopete could u e-mail me the pages out of the EVTM i would need? would really appreciate it!

the wire from ur fuel relay goes directly to the inertia switch,maybe theres a problem where it comes through the fire wall. my inertia tested okay but it kept tripping for no good reason.good luck

well it died again, had one of the tow trucks from work tow it in for me
i took a better look at the wires and the diagrams i have are all wrong, so i called a riend at ford to see what diagrams he could dig up
but im getting continuity between 2 wires of the fuel pump relay, even when it runs, so im pretty sure its a wiring harness issue. but im waitin to confirm that so i can take a look at the ford diagrams.
ifs its a harness issue this thing is probably getting parked for awhile

PM Sent.

wow, of the 2 ford dealerships around here neither one has a manual for my b2 lol
what is it with ford and throwing out their manuals?

the diagrams you are looking at sound like thay are stating that the wire from the ecm tells the relay when it should be sending power. not how much, this is always 12V,check grounds and conections and chnge the relay.clean the terminals and use some dielectris grease, relays do not always last forever. they can cause these symtoms. maybe these are different than what you have. they are from alldata.

yeah, i have the alldata ones. the problem is that whats on the diagrams does not match what i see. the colors are different/wrong. ie i ahve 2 yellow wires coming into the relay, when theres ony supposed to be one. the orange/ight green wire i thought went to the inertia switch is really the tan/light green wire that comes from the ecm, but still has continuity to the swtich. the red wire has a constant 2 volts with koe off. and the orange/lgiht blue wire that is supposed to go to the inertia switch is really black, and there is only 1 coming out of the relay....
hence, im stumped. hard to work with wiring w/o the right diagrams

ok, so i spent the first hour i was at work workin on this thing. i spliced in a new wire from the black wire coming out of the relay(the wire that goes to the switch) to the pink/blck wire(that goes o the switch) trying to bypass te bad section of wire that is shorted. basically i just jumped power out of the relay to the switch.
yeah, that didnt work. there was 12v in and out of the switch but the pumps wouldnt run.. there has to be another relay in there somewhere, which makes no sense.
....why couldnt this be an 89 b2?? lol