no power to fuel injector fuse

[samoyedman]

Changed 3.7L motor in my 2002 liberty, installed new crank and cam sensors, and it will start with starting fluid or gas, but will not start on it's own. Fuel pump is running, have over #40 of pressure. Checked the injectors with a noid light, no signal. I do not seem to be getting power to my injector fuse. swapped ASD relays and no change. I am getting a wiring diagram soon, but does anyone have any thoughts ? Thank you.

 

[Leeann]

I haven't checked the specs on the Liberty, but 40 psi sounds a little low. My GMs require 60+ psi.

 

[Billwill]

Do you have the SKIS anti-theft system installed/

ie. when you turn on the ignition is there a "key" symbol with a bar through it that light up for a few seconds.

If it flashes at you or stays on all the time then you have a SKIS problem ie. try using another chipped ignition key.

You can force +12 volts onto the relevent fuse by jumpering pins 30 and 87 in the ASD relay socket...will get you +12 volts on all the injectors but may not fire if if the SKIS is not happy or you have a cam/ crank sensor issue for instance.

 

[k99jk99j]

I beleive fuel pressure should be 49 + - 5psi.

 

[samoyedman]

I see no "key" symbol showing up at all. I jumped the 30 and 87 pins and got power to the fuse. Still no power to the injectors. If I had a cam/crank sensor issue, I would think that I would not get fire to the plugs. as I said it will run on starting fluid. Am I correct to assume that if I am getting less than 43 psi of fuel, that the fuel pressure regulator won't charge the injectors ?

 

[samoyedman]

Anybody ?

 

[Billwill]

I see no "key" symbol showing up at all. I jumped the 30 and 87 pins and got power to the fuse. Still no power to the injectors. If I had a cam/crank sensor issue, I would think that I would not get fire to the plugs. as I said it will run on starting fluid. Am I correct to assume that if I am getting less than 43 psi of fuel, that the fuel pressure regulator won't charge the injectors ?

If you jumpered pins 30 and 87 in the ASD relay you will definitely get +12 volts to the common side of the injectors....with respect to ground/chassis.

The Injectors get "fired" by the negative side of each injector being switched down to "ground" by the PCM using Pulse Width Modulation. The only real way of testing the injectors is by using an Oscilloscope over each injector....you "may" see something if you place a small light globe over the injector...directly across the injector...not using chassis ground.!

You need to see why the ASD relay is not energising....posssibly because the PCM is sensing a low fuel pressure?

 

[Billwill]

Stupid question maybe...I do not know the 3.7 gasser too well.

Did you put in a newer 3.7 engine to replace the original 2002 engine?

Reason I ask is that I have read reports that you cannot do a straight swap...there is some form of timing ring located on the end of the crank (reluctor ring)that needs to be replaced at the same time to get the new engine to work and possibly something on the passenger side camshaft!

I know you have stated that you replaced the crank and camshaft sensor so maybe this is what this link is about?


here is a link to replacing the older 3.7 engine with a newer one:

http://www.jeepkj.com/forum/f202/engine-swap-overview-53270

 

[samoyedman]

I am familiar with the engineering change with the '04 motors, and this is a late '03. I have used 2 different '02 and '03 ECM's to try to get them to charge, I am getting a rebuilt and updated ECM this weekend. Up until this point, I have not been able to get the injectors to charge. maybe it is a broken wire, I will look this weekend, but my question still remains, if I have #43 or less of fuel pressure will this not let the the injectors charge ?

 

[samoyedman]

anybody ?

 

[Billwill]

anybody ?

Do you have the Service Manual for that year engine?


you can download it here:Index of /manuals/Jeep/KJ

 

[samoyedman]

Sorry for the late reply, work has been busy. I do have a service manual I downloaded off of scribd, and have been looking at the wiring schematics. I checked the fuel pressure at the rail, and got a solid 49 lbs. under crank. Still n no signal with the new ECM. I am thinking I am going through the wiring harness this weekend, and check for breaks.

 

[k99jk99j]

Sorry for the late reply, work has been busy. I do have a service manual I downloaded off of scribd, and have been looking at the wiring schematics. I checked the fuel pressure at the rail, and got a solid 49 lbs. under crank. Still n no signal with the new ECM. I am thinking I am going through the wiring harness this weekend, and check for breaks.

Start with powers(plural) and grounds to the ecm.

 

[hilltopmike]

first you need to find out if you have a 5 volt reference signal to cam and crank if not unplug sensors one at a time if you suddenly get 5 volt signal that sensor is shorted out also make sure you have good ground Chrysler vehicles are picky sometimes on batteries and connections. does odo read NO BUSS ?

1. Check the year of the engine. The VIN is on the right hand side of the block just ahead of the motor mount.

2. If the 10th digit is a 3 or higher, the engine will not work in a 2002 or older vehicle with a Jeep/Truck Engine Controller (JTEC).

3. If the tenth digit is a 2 and the engine is from a Durango, the Camshaft Position (CMP) sensor tone ring should be inspected to be sure it matches the tone ring in the original engine. The Durango could be either an early design or a later design.

Tech Tips:

The NGC computer has 4 connectors and will not work on an engine built for a JTEC computer. The JTEC computer has 3 connectors.

 

[samoyedman]

I pulled the engine myself from a late '03 liberty. I think it was built in may of '03. I will check all of these suggestions before going in to the wiring harness. Thanks.

 

[samoyedman]

Checked everything you suggested, and everything was in spec. Then I started going through the wiring harness, used a jumper wire in both sides of the injector fuse, hooked up to a needle to probe for a signal in the orange/green main wire for the injectors. I pushed it in to a wire by the firewall first. To my amazement, I got a signal, and the car started right up. While I was admiring my genius, I put the car in gear to see if it would move, it did, I got out while it was still running, pondering a rewiring, when I looked down to see my jumper wire had fallen off, and the car was still running. Hummm. turns out dirt and corrosion has accumulated at the fuse slots not allowing a fuse connection. By forcing a wire in the fuse slot, it cleaned it enough to allow a connection. I replaced the fuse, and it runs fine now. My last question is what is the best way to clean the fuse blade slots without forcing them apart and having a loose fuse connection ? I thank everyone for their input, because sometimes just talking to someone can give you ideas.