1987 Pathfinder injectors not working? Injector Circuit Open?

[maswart]

Hi all -

 

I have a 1987 pathfinder with the 2.4 engine. I'm having an issue getting it running again. It seems like there is no fuel coming out of the injectors. There is fuel pressure. The fuel pump is working. I checked the ECU code and it comes back 43 which is either Open Injector Circuit or Throttle Position Sensor. It will start with fuel in the throttle body or starter spray but dies out as soon as that burns off. I feel like it is an electrical problem, because my son may or may not have jumped the truck off backwards at one time or another. Before that it was working fine. I thought I would find a blown fuse or relay, but so far I've found nothing amiss. Checked relays with 9v battery and multimeter. Any ideas on where to start? How to check signals to the injectors? Check the throttle position sensor? I'm not sure where to go next.

 

thanks!

[Slartibartfast]

The '89 manual shows a safety relay, which I'm pretty sure is supposed to protect the electrical system against what your son may or may not have done. Wouldn't hurt to check the fuse links (near the + battery terminal) though.

 

Code 43 shows as throttle sensor in the '89 and '95 manuals. The '89 manual shows just a potentiometer inside the TPS, so testing between the two outer pins should show a constant resistance, and testing between either outer pin and center should show a resistance that varies as the throttle is opened or shut. Now that I think about it, I have heard of some vehicles shutting off the fuel injectors during startup if (it thinks) the pedal is held to the floor. I have no idea if the '87 Z24i was set up with that kind of thing, but it's certainly worth checking.

 

I would also want to check the injectors and their wiring for any obvious rodent damage, and test for open circuits with a multimeter if possible.

[maswart]

Thank you for the information. I pulled the safety relay and it seems to be functioning appropriately. I also pulled the connector to the TPS but there are only two wires in that harness. All the fusible links and relays that I can find are still good. I was thinking bad or damaged ECM, but it does change modes appropriately and display trouble codes when cycled. I'm going to poke around on it some more today.

[byob]

The injectors are "live" with power all the time. The ecu grounds the injector for pulse. First thing I would check is the power to the injector

[maswart]

So the shop found damage chips in the ECM. One cracked and one melted. These are injector circuits we think. I am having trouble locating a replacement though. I want to go salvage, but so far I can't match up the numbers. Do you know if another one might work. Mine is an MECS-G101 D1. Its in a 1987 pathfinder 2.4L with manual transmission. I have located another for an 87 pathfinder manual tranny. Its number is MECS-G120 D1. I think its probably worth a try. Anybody have any more information? Thanks!

[RCWD21]

As long as it's from a z24i pathfinder or harbody it will work just fine. Doesn't matter if it's manual or automatic transmission. Luckily since you have a manual transmission you can pick from either or. If you had an automatic then you'd be strictly limited to automatic vehicles.

 

As a side note, make sure the ecu is from a z24i vehicle. The plugs are the same configuration for the vg30 powered rigs.

Edited August 6, 2016 by RCWD21