ot question for mechanics

[poomwah]

Please help with diagnosis. Mary ann drives a 98 merc mystique 6 cylinder.

We stopped for gas today, car started fine, but when we pulled out onto the road, it died.

The battery is good, but it won't crank over. Dash lights come on with key, but no usual noise frome fuel pump. Can't find any blown fuses. There is no powere getting to the fuel pump fuse. Starter tested out good, so did starter solenoid.

Any suggestions?

[rpsands]

Alternator? If this is the case you should be able to charge the battery and make it start.

 

There's no power getting to the fuel pump...hrm..sounds really familiar to me. I used to have a Nissan Altima that had a weird little electrical gizmo that we had to bypass (hardwire) to get power to the fuel pump. Some kind of electrical junction thing, it was like a cartridge of some sort.

[Trauma_Luna]

motor de arranque.. i dont know how to spell it in English ''starter motor'' maybe,,

[poomwah]

Battery is fully charged. Starter motor is good. Getting power to fuel relay. No ground on fuel relay though. I can hardwire the fuel pump, but it still won't crank

[MarvinDog]

I seem to remember something about faulty ignition switches on Mystiques/Contours. Then again, I could easily be mistaken.

[Orph]

I'm thinking the switch behind the key to the ignition, or maybe the fuel pump relay.

 

Try force-running the fuel pump by hooking it up directly to the battery first of all, just to eliminate it as a source for the problem (I can't figure out if you've actually tested whether the pump gets any power at all, or if you're just supposing that it isn't).

[solderjunkie]

Driver side under the hood. Pull the fuse panel cover off and yank gently on the wires coming out of the back of it.

 

They are bad about scorching the fusebox connections when the fan/defroster are on full blast.

 

If it starts while wiggling the connectors, lift the fuseboxout and repair terminals as needed:thu:

[t3ch]

I have the diagnosed the problem of you having a '98 mercury. I'm... I'm so sorry.

[perrydabassman]

Sounds like the ECU, or the fuse supplying it. The Electronic Control Unit on automobiles nowdays controls everything. It tells the pump to turn on and prime the system when you first turn the switch. When it sees sensor activity on the flywheel, it tells the ignition to fire. If you are getting nothing but your voltage is at the relays, it is more than likely the ECU.

[poomwah]

Thanks guys, I've eliminated the following

Battery

Starter and solenoid

Fuel pump,(if I bypass the relay it pumps)

Fuel pump relay

Starter relay

Ignition switch. If I turn the key on, I get power to the fuel pump relay

If I turn to the start position, I get power to the starter relay.

No ground to the fuel pump relay or starter relay. If I bypass them the pump works, and the engine cranks, but won't start.

So I'm probably not getting ground to the ignition relay either, still looking for that one

[solderjunkie]

Is the "security light" on the dash flashing when you try to start it?

[perrydabassman]

 

Thanks guys, I've eliminated the following Battery Starter and solenoid Fuel pump,(if I bypass the relay it pumps) Fuel pump relay Starter relay Ignition switch. If I turn the key on, I get power to the fuel pump relay If I turn to the start position, I get power to the starter relay. No ground to the fuel pump relay or starter relay. If I bypass them the pump works, and the engine cranks, but won't start. So I'm probably not getting ground to the ignition relay either, still looking for that one

 

 

See post above this.

[poomwah]

Sounds like the ECU, or the fuse supplying it. The Electronic Control Unit on automobiles nowdays controls everything. It tells the pump to turn on and prime the system when you first turn the switch. When it sees sensor activity on the flywheel, it tells the ignition to fire. If you are getting nothing but your voltage is at the relays, it is more than likely the ECU.

 

That's what I was worried about. And unfortunately the fuse is good

[perrydabassman]

That's what I was worried about. And unfortunately the fuse is good

 

On alot of them, you can just replace the EPROM. Waay Cheaper than the whole ECU. And you might look at the salvage yards for a wrecked one. If I remember correctly, I think the fords were up under the glove compartment, attached to the firewall.

[poomwah]

 

Is the "security light" on the dash flashing when you try to start it?

 

 

Security light goes out when I turn key on

[poomwah]

Does the ecu control the starter relay, it won't crank with the key

[bassman1956]

Fusable link?

[misterhinkydink]

In '98 Ford started using a fuel pump controller that gets a PWM signal from the ECM to control the fuel pressure. It doesn't just go on and stay on. I had one of these go bad on a '98 Escort and was able to troubleshoot it with a DMM. If your car has no fuel return lines it uses this system.

[ec437]

It is possible that the ground for the fuel pump relay is controlled by the ECU, or it could be controlled by another relay. I believe that on my car, the main relay (which is controlled by the ignition switch and security relay) controls the ground for the fuel pump relay and injection system.

[solderjunkie]

 

It is possible that the ground for the fuel pump relay is controlled by the ECU, or it could be controlled by another relay. I believe that on my car, the main relay (which is controlled by the ignition switch and security relay) controls the ground for the fuel pump relay and injection system.

 

 

The main relay supplies power to the coil in the relay, the security/central locking unit provides ground... if it has the passkey system (security lamp on dash).

[solderjunkie]

I know you said the dash lights come on... what about the check engine light???

 

if there is a check-engine light, the PCM likely has power.

[poomwah]

So since its the starter relay and the fuel pump relay, I'm leaning towards security

[poomwah]

Dammit is cold out there andSTILL snowing

But I figured I would check a few things that you guys suggested

NO check engine light

[solderjunkie]

Dammit is cold out there andSTILL snowing But I figured I would check a few things that you guys suggested NO check engine light

 

gimme a sec to scope out the schematic...

 

edit: You got a test light?

 

fuses 1, 4, 9, 13, 14 under the hood.

 

fuse 1, battery power

 

fuse 4, power with key on (tests ignition relay under dash)

 

fuse 9, battery power

 

fuse 13, power with key on (tests PCM power relay)

 

fuse 14, power to prime fuel pump when key is cycled (tests fuel pump relay)

[ec437]

 

No... the security/central locking module grounds the starter relay. I looked at the schematic... this one is old-school relay. The main relay supplies power to the coil in the relay, the security/central locking unit provides ground... if it has the passkey system (security lamp on dash).

 

 

Ah ok. I had that problem in my car; I ended up using a paper clip to bypass part of the security relay so it would trip and provide ground to the fuel system relay(s) when I had the ignition turned on. Maybe the OP will have to do something similar.