Sorry - ZXT swap troubleshooting

[afbrian13]

again right....

Yes - I've searched and searched but still need to post a question

what I've got..

76 280z 5speed with 83 zxt swap. all emissions are hooked up still

i drove the donor car(guy was doing a v8 swap and didn't want the engine)

ran great in donor car, pulled the engine without disconnecting any wiring from the engine itself (flipped everything on top and tied it on-really helped when the time came to lay everything out in the 76)

put everything together with stock parts and the car runs but...

 

the problem

it runs so rich that it floods itself out idling warm or cold, i've checked all the connections, ohmed everything from plug back to the computer and all checks good. everything has proper grounds. no leaks on the intake, but the tube is longer now then stock so it would fit.

 

i'm running the 76 fuel pump, but can't imagine it putting out more psi than the 83

the AFM or computer could have been banged i suppose

does it sound like the computer is in "limp" mode?

is there some wire that i missed when i spliced the harneses together?

can you test the computer itself?

what do you think? I've tried the usual stuff(connections, temp sensors, grnds) its killing me that it runs-sortof, and not quite well enough to drive

 

if you run it hard it can almost burn all the fuel but smokes like hell when you let off the throttle. I've pulled the plugs after it idles awhile and they are soaked.

should i get a different ECU or AFM, or try one of the 300zx computer conversions(what are the actual advantages to this btw)

what is the absolute minimum this engine needs to run well (i don't care about passing smog tests)

 

sorry for the length, but I'm finally asking for help. Its driving me nuts that I can fix a jet (I'm active duty USAF) but not my baby

also i tried to limit my questions to things i've searched over and over and couldn't find a good answer for or was still a little confused about.

 

thankyou very much and can't wait for an answer back

Brian

brian.powers@offutt.af.mil if you want, or have anything that might help(diagrams, charts - I'm open to anything at this point)

[VinhZXT]

This sounds like the AFM is the problem. Unplug the AFM connector and check for resistance of all the wires from there and back to the ECU. Check to see how stiff the flap inside the AFM. If it's too loose then read the manual for procedure to test out the AFM. And last clean out the ECU connectors real good and put some conductive grease on the pins and connectors. Good luck

[Thumper]

Also check the head temperature switch. It is on the passenger side of the engine near the fire wall. I would also check the coolant temp switch. Its on the thermostat housing. It is the passenger side sensor with two wires.

[SleeperZ]

Did you carry over the ignition? I had plug wires go bad on me with my stock ZXT install using the Z coil, and it would run semi-ok until I loaded it, then it would misfire like mad and soak the plugs in fuel. I had it figured for running too rich as well before I discovered the ignition issues.

 

Not that it couldn't happen, but I've never seen an AFM go bad in that way (or a ECU). Don't worry about the pump, the regulator on the fuel rail regulates fuel pressure for you, and if it worked before the swap, it's unlikely to have failed on you. However, a bad pressure regulator will cause it to run pig rich even if the diaphragm doesn't rupture and flood the intake manifold insides with fuel.

[afbrian13]

Thank you very much for responding. I'm completely open to ideas at this point.

 

I was just in the garage. I tried starting the car but all it would do was crank, but sounded like it was trying. Checked for spark (which was there), and could smell i had fuel. I had a friend crank the engine while i worked the flapper on the afm by hand. with it pushed the engine would start to crank but not quite fire, but with a little throttle it started and ran, although very rough, and rich enough to smoke up everything. I tried driving it but it had no power. you could rev it slowly but it sounded rough.

i checked the wiring and everything ohms good back to the ECU

 

I pulled the vacuum line off the fuel PSI regulator, sucked on the vacuum line, but nothing changed. BTW, before it started playing with the regulator didn't change anything.

 

However, I pinched the fuel line itself and the idle smoothed out and i could rev the engine closer to normal, but it was still rich.

 

Any more ideas guys?

Thanks in advance!

 

sleeperz - i didn't even touch the ignition system when transplanting the engine

[cygnusx1]

1) Good electrical grounds and EFI connectors clean and lube

2) fuel pressure 30-35 psi steady- put gauge at fuel rail entrance.

3) ignition and timing 20-23 BTDC

4) compression test 145-155psi

5) vacuum/intake leaks (very tough to find)

6) cam timing

7) all injectors working?

8 ) clean "slider" inside AFM cover

9) 12volts supply solid at ECU?

 

TPS, AFM, HEAD-TEMP, O2...all sensors and intake manifold "vacuum doo-hickies" working OK?

 

Is your water temp gauge working?

 

Is your Tach working?

 

That's my hitlist for now. Good luck and keep us updated.

[afbrian13]

Thanks again.

 

Earlier i was getting some funny readings with a multimeter, and decided i was going to solder everything instead of using plugs. This should eliminate some problems.( after testing each component first)

 

Can i get rid of the canister,the 2 vacuum solenoids, vacuum rail(for lack of better term) on intake, and the hoses coming from each as long as i put caps over all the nipples?

I don't care about emissions, so knowing that what are the minimum sensors this engine needs to run well. Just figure i can eliminate possibilities.

 

Is there any of you that have done the swap and/or installed a MS&S system on your car that would be willing to talk on the phone? Some things are easier that way. As always, thanks a ton for your help. I want my baby back on the road

[Turbo280Z]

i jus finished my turbo swap on my 78 280z. it also runs WAY rich and it only runs good if its around half throttle.it might be my coil. im using a msd coil im going to try the stock one tomorrow see if that helps any. or it might be the ecu. mine came from an auto and now its manual. what ecu are you running?