Injectors not firing

[moalaska]

I have the unicorn 1986.5 electro injection z24.  It's hard to find any tech manuals for this.  Anyway my injectors arent firing for the tbi.  I suspected a fusible link but they all check out continuity and I short wired every one just to rule them out.  Fuel pump runs.  Engine runs if fuel dumped in Tb.  It's an electrical issue.  I have code 23 and 24, my clutch switch never worked and I was able to start without pushing clutch.  So what would prevent injectors from firing?  Is there a ground Wire related to the tbi that might need cleaned?

[datzenmike]

 

 

I'm afraid all I have is the 86.5 mid year supplement for the D21 Hardbody and there were some significant changes to the Z24i after the 720. For one, there is no code 23 and the clutch switch should ground when depressed or the starter does not engage. The 720 may be different?

 

Clean / check the TBI electrical plug and make sure the TBI is grounded.

 

Do you have fuel pressure at the TBI? Not saying to change the fuel filter but could it or the lines be blocked?

[moalaska]

Starter cranks, clutch switch didn't work before so I'm assuming that isn't issue.  Fuel pump primes when keyed on and after cranking.  I guess I'll have to pull fuel line at Tb.  This happened right after getting gas at station so maybe their gas had some junk in it.

[datzenmike]

Gas not diesel by mistake?

 

Direct fuel (from filter hose, easier to get at) into a container and see what comes out. There would have to be a lot of water in the tank to reach the pick-up tube. If water you'll have to drain the tank of it before continuing. At least the 720 had a drain bung and water is heavier than gas so it should come out first.

 

Water is 'thicker' than gas and might 'clog' the injectors or maybe the filter. 

 

You should be able to see something spritzing out the injectors. It won't be much just for idle. If water it will clear itself but may take a long time.

[moalaska]

I think it's electrical though.  After it died I fiddled with wires and different things and it eventually started.  It ran for 3 hours but when I shut it off wouldn't restart.  I'll still check the fuel, but seems like a faulty electrical connection or bad ground or something else.  I suspected fusible links but like I said, I checked them.  

[datzenmike]

 

Always include all information.

[moalaska]

I pulled the fuel lines.  Both absolutely dry.

[moalaska]

On the fuel pump, does the supply go in the bottom?  And is the fuel filter pre fuel pump or after the fuel pump, it's hard to see with the hoses going behind the frame

[moalaska]

Between the outlet of the fuel pump and  inlet of fuel filter, by the frame rail, it appears there is some other component where I believe there is a blockage.  I get no fuel out of fuel pump.  I tried fishing some trimmer line in the hose but it will not go through this section.

[moalaska]

I can reach my hand back there, it feels like a fuel damper

[datzenmike]

I would assume that there is a fuel filter between the tank and the electric fuel pump. Follow the fuel line back and if you find one replace it.

 

 

It's odd this happened just after filling up. This would be the time dirt and crap could get it and clog the filter. Cheap fix if this is it.

[moalaska]

So following fuel lines, tank outlet goes to bottom of pump inlet.   Then from pump, into fuel damper, from that to fuel filter, then to fuel line to engine.  I bypass the fuel damper but I'm still not getting my truck to fire. When I pulled the hose off the bottom of the fuel pump fuel did pour out slowly out of the hose. Maybe that's blocked somewhat and preventing the pump to build enough pressure. I'll have to fiddle with it some more tomorrow, this would seem like it would be a simple fix. I wish there were more Tech diagrams for this thing.

[datzenmike]

Pull the hose off after the fuel pump and try it. If it pushes fuel the blockage is ahead of it. Damper or fuel filter (which by definition filters and gets plugged and why it should get replaced every 2-5 years)

[moalaska]

I replaced the fuel pump and filter just now,I will pull hoses tomorrow and try and narrow it down.  

[moalaska]

No fuel out of pump, no fuel out of tank.  I should have at least a gallon in there.  Maybe partial blockage in pickup and can't get siphon effect going.

[moalaska]

Is there a filter screen or anything inside the tank pickup?

[datzenmike]

10 minutes ago, moalaska said:

No fuel out of pump, no fuel out of tank.  I should have at least a gallon in there.  Maybe partial blockage in pickup and can't get siphon effect going.

 

A gallon???????????? Try putting some gas in it.

 

[moalaska]

fuel pump polarity was reversed, I dont know if nissan has backwards colors for wiring or maybe a previous owner put a red wire for black and a black wire for red, explains when I installed new fuel pump I couldnt get any gas to go through it.  runs like a charm now.

[datzenmike]

Nissan always uses Black for grounds.