No fuel at the plugs

[lyttlea]

Hi everyone, I wonder if you can help?

I have a challenger 2000 with the merc 240EFI, the earlier model with the stator.

I have a good blue spark, 36psi on the fuel pressure, I can hear the lift pump and high pressure pump working but I have bone dry plugs? It doesn't even try to start.

The problem occurred last week, the fuel pumps were not turning on, that turned out to be a bad wire in the harness (pin 11), the red yellow to the solenoid. I replaced it as well as the earth pin 16.

I checked all 16 wires in the harness and they are now all good. I took the manifold off and the injectors all read the same resistance I also preformed the test in the manual. The injectors seem clean and functioning. I had also replaced the ECU the week before so I know that's good. What could I have done in replacing those two wires that is stopping fuel delivery? I seem to have fuel all the way to the rail.

Oh and I also checked the compression it was 105psi on all cylinders. I know that's low but I'm hoping that's because it's cold or a bad gauge as they where all balanced and it was running ok before.

Thanks in advance

Alan

 

[Dr Honda]

The ECU controls the ground on the injectors. Is there power on them?

 

[Sportster-2001-951C-Stock]

Yep, measure and see if there's 12VDC to ground on the injectors.

 

[lyttlea]

Yep, I have 12v to the injectors. This has me stumped!

 

[Dr Honda]

Just for giggles.... Spray in a little starter fluid, and see if she fires. If it does... then we know it's fuel. If it doesn't... then it could be ignition or the low compression.

Since the compression is low, and we think it could be just a bad gauge... test it on a known good running engine.

 

[Coastiejoe]

I think the injectors are "negatively activated", which would mean that you would have 12 volts to them but still not work as the negative side is triggered by the MPEM.

Best way to test that system is with a Noid Lamp.

 

[lyttlea]

Ok guys, I went in! I took the manifold off but left everything else connected so I could visually see if the injectors are firing, none of them are. I have 12v so as you say costiejoe it must be the grounding. MPEM test. Is that his the ignition module box on the top of the engine?

 

[lyttlea]

Just checked the compression with a different gauge and had 130psi on all 6 cylinders so that seems fine.

 

[Coastiejoe]

Get an adjustable noid lamp. They work on anything. Like $25.

This will tell you for sure if the injector pulse is being sent.

 

[lyttlea]

I took the injectors out of the fuel rail and tested them individually by hooking them up to 12v battery and forced fuel through them. They all worked fuel passed through when it had 12v on it.

So I have:
- clean injectors
- all injectors work when tested with 12v individually
- 12v is defiantly getting to them

This must mean the yellow, blue and white wires are not grounding them. Any ideas? Other than the ECU, what would cause this?

 

[Coastiejoe]

I don't know much about the specifics of the Mercury, but I do know about late model engines.

Most injectors are signaled on by the main brain. However, they are looking for input from a cam sensor and a crank sensor.

If the Mercury has these sensors, you can unplug them and put a DVOM on A/C and crank they engine. If the sensor is good, it will show low A/C voltage on the DVOM.

 

[Dr Honda]

I would hook an O-scope to the wires on the ECU for the injectors, and see if you get any signal.


BUT... did you try the starter fluid thing yet? Just to see if the engine will make noise?