Fuel injection troubleshooting

swl · 09-17-2005, 12:34 PM

Hi guys. I've just about done all I can think of to figure out what is going on with my D-Jet. Running out of ideas and desparately need help.

This is a 73 1.7 - bone stock that hasn't been fired up in 20 years. There is no firing pulse arriving at any of the injectors. The saga began when I pulled the injectors out to look at spray pattern. They were spitting just the tiniest little bead so I took them out to clean them. Note though that they were spitting - so I must have had a firing pulse. Wound up sending them to a pro who did it on a ultrasonic machine. They are now tested and working great. Reinstalled on the rails and looked for the spray pattern. Nothing. Operated it with a 6volt lantern battery and it sprays just fine. But a voltmeter on the fi plug to look for the pulse. Nothing.

Pulled the diz and cleaned the points there. Confirmed with an ohm meter that 21-12 closes for one half the revolution of the rotor and 22-12 closes for the second half.

Checked for power on T4-I of the relay board. Checked continuty of harness between T4-I and the ECU.

Checked ground wire on the FI plug.

Checked continuity of the hot wire on the fi plug back to the ECU.

All of these are showing correct.

What else could stop the ECU from sending a pulse?

Dave at Pelican Parts · Dave at Pelican Parts's Garage

Check all of the wires in the engine bay. There are a number of them that, if unplugged, will keep the injectors from opening at all. The main ones that come to mind are the ones to the Manifold Pressure Sensor (MPS)--the silver hand-grenade thing on the right side of the engine bay--and the ones for the trigger points in the distributor.

It's easy to disturb the wires to the MPS when you're mucking about with the injectors on the right-hand side of the engine.

--DD

swl · 09-18-2005, 08:58 AM

Thanks Dave, I think you may be right. Measured between pins 8-10 on the ECU end of the harness and found it open. At the mps it's 30 ohms. Waiting for my son to get home so I can confirm.

swl · 09-18-2005, 10:07 AM

actually - 300 ohms - didn't apply my scale.

I think I have it down to the #10 wire (those white ones are all appropriately labeled on their jackets!) right at the spade connector at the MPS end. Is there anyway to take the wires out of the connector? Obviously they were originally crimped and pressed in but should be be able to push them back out without mangling something?

Dave at Pelican Parts · Dave at Pelican Parts's Garage

Look in the end of the connector. You'll see that for each pin, there is a notch sticking up from the slot. (Or down, if you're holding it that way.) That is where the retaining barb for the metal pin is. You can carefully reach a thin piece of metal in there to press the barb downward against the rest of the metal pin, and pull it out the back side of the connector.

New metal pins are available from Beck-Arnley, a common parts distributor. Your FLAPS may be able to order them. I used to have the part numbers saved, but I cannot find them any more.

If you can score the metal part (you can substitute a barbed 1/8" female spade terminal; it's almost but not quite the same) you can crimp it on the wire. You need to make a very very good connection there, so crimp tightly. Using a good crimping tool is the best bet.

--DD

swl · 09-18-2005, 01:34 PM

got it. Thanks Dave. The wire was broken right at the spade. I suspect that when Devon was trying to take the wire off to get at the injectors that he had a pull on the wire instead of the connector. Caught myself doing the same thing when I was tearing it down for testing. It was hanging by a thread.