Fuel Problem

dlawler2 · Aug 20, 2008

Hey guys-- long time lurker first time poster here. About a week ago I went to start up my car and got nothing. I didn't hear a fuel pump prime so I assumed it was that. I replaced the fuel pump, the fuel pump relay, and reset the inertia switch in the trunk and I've still got nothing. The thing ran like a champ up until then and I really don't even know where to start now. Any suggestions?

LiquidGT · Aug 20, 2008

Welcome.

Did you check the fuse link on the starter solenoid? It would be on the orange/lt blue wire.
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

dlawler2 · Aug 20, 2008

If I was to run a wire bypassing the fuse link would this be sufficient to get the fuel pump to run if the fuse link was the problem?

dlawler2 · Aug 20, 2008

Also-- How would I know if my fuel inertia switch is still good? This all happened after a slow-rolling nudge into a trailer hitch(caught my license plate luckily), so I'm still not 100% its not the inertia switch.

HISSIN50 · Aug 20, 2008

Rather than jumping around, run the checklist. It goes quickly and will tell you what part of the circuit to troubleshoot.

LiquidGT · Aug 20, 2008

I the fuse link would be burnt up if it was bad, don't bypass it or you won't have any protection.

There is a way to jump the fuel pump to test it on the EEC IV test connector. The checklist: http://forums.stangnet.com/6161267-post.html

I got into a tail light smasher a coulple of months ago and my inertia switch popped, but the button was stuck in the "working" position. So I had to hit it with a blunt object so the button would come up, then I could push the button back down to reset it.

BlownFiveLiter · Aug 20, 2008

It sounds like your stator is probably bad in the distributor. A quick way to test that is to see if you have spark or injector pulsing, too. You'll need a noid light to check the injectors.

dlawler2 · Aug 21, 2008

StangGT1995 said:
It sounds like your stator is probably bad in the distributor. A quick way to test that is to see if you have spark or injector pulsing, too. You'll need a noid light to check the injectors.

I checked it for spark and got it so I don't think that's the problem. With the inertia switch what is the correct position of the button? Right now the button on mine springs up whenever I push it down. I've never dealt with one of these before so I was just assuming this is right, but is it?

LiquidGT · Aug 21, 2008

The switch should click when you press it down, then if you smack it hard enough it will pop back up. If you tried everything else then get another switch from the junkyard for cheap.

dlawler2 · Aug 21, 2008

Ok I wanted to make sure I was getting power at the right spots so I busted out the voltmeter.

At the fuel relay I got Orange/Blue:12V Pink/Black:6.7V(key on) Red/Black: 12V(key on) and what looks like beige:1.2V (key on)

At the inertia switch I got 1.2V on the left terminal and 12 on the right.

I popped the inertia switch with a shoe and then reset it and tested the resistance. It was at zero ohms so I think that's okay. Guys I appreciate the help you've already given me and if anyone can see anything wrong with these numbers please just let me know.

HISSIN50 · Aug 21, 2008

Did you tell us what year car you have? The location of the inertia switch in the circuits changed over the years.

Retest the inertia switch. You should have nearly no voltage drop across the switch.

dlawler2 · Aug 21, 2008

Sorry guys it's an 89 hatch.

dlawler2 · Aug 21, 2008

Okay if I take the two leads of my voltmeter and put them in the input terminals of the inertia switch i get a volt reading of 10.3 or so. Apparently it should be 0? Where would I go about looking for the cause of the drop?

HISSIN50 · Aug 21, 2008

Check the instructions for using your meter. If you put one lead on the input and one on the output (with the meter set to DC volts), you'd see the voltage drop across the inertia switch. The reading should be tiny (something along the lines of 0.10 volts or less, though I haven't tested one before).

If this is what you did, you have a difference of 10.3 volts (10.3 more volts going into the switch than coming out). That's no good. Recheck your reading. Ground the neg meter lead and probe the in and then the out terminal. Compare readings. They should both be near battery voltage (12.0-12.6 volts or so).

dlawler2 · Aug 22, 2008

HISSIN50 said:
Check the instructions for using your meter. If you put one lead on the input and one on the output (with the meter set to DC volts), you'd see the voltage drop across the inertia switch. The reading should be tiny (something along the lines of 0.10 volts or less, though I haven't tested one before).

If this is what you did, you have a difference of 10.3 volts (10.3 more volts going into the switch than coming out). That's no good. Recheck your reading. Ground the neg meter lead and probe the in and then the out terminal. Compare readings. They should both be near battery voltage (12.0-12.6 volts or so).

Okay I grounded the neg lead and probed the in and out. I got 11.7 or so in and 1.2 out so a difference around 10 again. I have no idea what would even cause this-- would a break in the circuit somewhere lead to this?

I also tried grounding the fuel pump test point and didn't get anything.

HISSIN50 · Aug 22, 2008

dlawler2 said:
Okay I grounded the neg lead and probed the in and out. I got 11.7 or so in and 1.2 out so a difference around 10 again. I have no idea what would even cause this-- would a break in the circuit somewhere lead to this?

I also tried grounding the fuel pump test point and didn't get anything.

If you are dropping 10 volts across the inertia switch, reset it and try again. If you still have the drop, that suggests the inertia switch is bad.

86foureye · Aug 22, 2008

make sure the ecm relay is working too. the relay by the computer

HISSIN50 · Aug 22, 2008

86foureye said:
make sure the ecm relay is working too. the relay by the computer

He said he has spark, and that he has 12 volts into the inertia switch. Both of those would be absent if the EEC relay was bad.

dlawler2 · Aug 23, 2008

Okay guys here's what I've got now. Apparently the pump is getting some power, but not enough to run it. It's getting 6.3 V through the pink/black wire (I'm getting that at the relay and the pump itself). Any ideas of what could be going on here for me to only be getting half the power I need?

dlawler2 · Aug 23, 2008

Also, even when the relay is unplugged I'm getting 6 volts on the pink/black wire under the seat and at the pump. Shouldn't this be 0 w/o the relay in since its basically just a wire running from the relay to the pump?

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