# engine cranks, runs on ether, won't run on fuel



## BeyondBiscuits2 (Jan 18, 2006)

I need some help from the Z31 gurus. I have a 1985 Nissan 300ZX 2+2 whose engine jumped time last year. I pulled the engine, and did a once over on the whole powerplant. Heads came off, went to the machine shop (pressure checked, dipped, and decked), no bent valves. I reassembled the engine (new front and rear main seals, intake gaskets, head gaskets, timing belt, water pump, etc.). She cranks like a champ, and tries to give it a go, but won't run on petrol. Spray some ether in there and she comes to life and sounds great in the process. We've tried fiddling with the distributor (making sure it wasn't off a tooth). It has fresh petrol in the tank, and a brand new fuel filter. Any idea on what could be causing it not to run? Compression is good on all 6 cylinders, by the way. The timing belt was installed by a professional Nissan Master Tech, and the distributor is a little over a year old and is an OEM Nissan part. The ECU is not throwing any codes. Fuel pressure post filter was spot on, but I can't confirm after the FPR. Also... can anyone take a picture and post it of their distributor rotor button at TDC? I'm going off what the Haynes manual says with the button being past no.1 cylinder...


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## smj999smj (Jan 1, 2006)

You said that when you spray either in her, she "comes to life and sounds good." This would elimate an ignition system issue and make it a fuel delivery issue, so you can stop "fiddling" with the distributor. You claim you tested the fuel pressure and it was good, so that eliminates the fuel pump, meaning it is likely that the fuel injectors are not "firing." Unplug a fuel injector on each side, turn the key "on" and use a 12V test light to confirm power at each of the injector harness connectors. If there is no voltage to them, you'll need to figure out why not? If there is power, use a "noid" light for Bosch style fuel injectors and install it in one of the injector harness connectors. Crank the engine and see of the noid light "flashes." If it doesn't, confirm the same on the other connector (the reason I say use one injector on each bank is because---assuming your vehicle has has the fuel injector campaign---all three injectors on each bank fire at the same time and each bank uses the same power and ground circuits). If the noid light doesn't flash, the ECM is not pulse grounding the injectors so it will not be injecting fuel into the engine. You'll have to check the circuits between the injectors and the ECM to make sure they are not shorted to ground (*Note: if your Z had the fuel injection campaign, check the circuits of only the middle injectors on each bank, because those wire the circuits used to install the update injector subharnesses). Since you already know the engine has spark when you tested it with the either, that rules out a crank angle sensor issue. So, if it's a injector grounding issue, it's likely open/shorted wire between the ECM and injectors, bad ECM grounds or a bad ECM. ECM grounds are on the intake plenum, IIRC. Make sure the connection is clean and tight.


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## BeyondBiscuits2 (Jan 18, 2006)

Thanks for the advice. My Z has had the fuel injector initiative performed. We've found the issue, fortunately. Looks to be the MAF sensor, though it isn't showing a CEL on the ECU, hence why I didn't mention it. We unplugged it, and the car runs great in limp mode, idles smoothe and everything. So... I'm off to find a new MAF. Hopefully this will eliminate the problem. Thanks for the quick response.


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## 300zxFan (Jan 15, 2013)

*Re- cranks, runs on ether, won't run on fuel*

I'm having the same issue. I can get it to run on ether but it wont run on it's own. I've just installed a new fuel pump and getting pressure. My car has the new injector harness updated during the injector recall. Ive confirmed that the injectors are getting the pulse, the noid light flashes. I'm going to try unplugging the MAFS to see if that helps but in my case this car has set for 10 yrs. I'm may have to pull the fuel rail injector assembly. I'm kinda strapped for cash at the moment so Im going to try this first. Fuel injector cleaning - YouTube I know it's kind of crude way of doing things but it cant hurt to try.


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## jdg (Aug 27, 2009)

The youtube video doesn't seem like tooooo bad of an idea.
One thing of caution. That guy is using a 12v battery to power the injectors. Injectors aren't held on continuously, they're only on for like milliseconds at a time. Hold them on much longer and you'll run a good chance of burning them out.
If it was me doing this (and I have an adjustable power supply), I'd only give the injector enough voltage to open up and that's it. No more. If you don't have access to one, try something like a 9v battery first and see if it'll open, or put a light bulb in series with the battery and injector. Anything to keep the full 12v from the battery from hitting the injector all at one time.


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## 300zxFan (Jan 15, 2013)

jdg said:


> The youtube video doesn't seem like tooooo bad of an idea.
> One thing of caution. That guy is using a 12v battery to power the injectors. Injectors aren't held on continuously, they're only on for like milliseconds at a time. Hold them on much longer and you'll run a good chance of burning them out.
> If it was me doing this (and I have an adjustable power supply), I'd only give the injector enough voltage to open up and that's it. No more. If you don't have access to one, try something like a 9v battery first and see if it'll open, or put a light bulb in series with the battery and injector. Anything to keep the full 12v from the battery from hitting the injector all at one time.


Thanks, I'll try the 9 volt first. I've got to get a momentary switch too. I was thinking at first to do away with the switch and just tap the wires together to make the circuit but then I got to thinking carb cleaner is combustible, I dont need to have sparks flying around


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## jdg (Aug 27, 2009)

300zxFan said:


> Thanks, I'll try the 9 volt first. I've got to get a momentary switch too. I was thinking at first to do away with the switch and just tap the wires together to make the circuit but then I got to thinking carb cleaner is combustible, I dont need to have sparks flying around


I wouldn't worry about the switch & sparks, and carb cleaner is a bit tough to get going anyways...not to say it won't catch fire, but you kinda gotta work at it.
And I was thinking about it a bit...a 9v battery will likely go dead pretty quick, if it works at all (I dunno, haven't tried it). Might be better off using a bunch of AA's...start stacking them up in series and keep trying until the injector fires and go with it. If you don't have a battery holder of some type, find a cheap toy that runs on 4 or 6 or 8 of them and hang a couple of wires off the ends with the "toy" off...just to have a battery holder that is.


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## 300zxFan (Jan 15, 2013)

jdg said:


> I wouldn't worry about the switch & sparks, and carb cleaner is a bit tough to get going anyways...not to say it won't catch fire, but you kinda gotta work at it.
> And I was thinking about it a bit...a 9v battery will likely go dead pretty quick, if it works at all (I dunno, haven't tried it). Might be better off using a bunch of AA's...start stacking them up in series and keep trying until the injector fires and go with it. If you don't have a battery holder of some type, find a cheap toy that runs on 4 or 6 or 8 of them and hang a couple of wires off the ends with the "toy" off...just to have a battery holder that is.


Perfect! It's an electronic surplus store in town, they should have everything I'd need. I'll check it out tomorrow and build a jig. I still have to brake down the intake to access the fuel rail assy. I might tackle this over the weekend. I'll keep you posted on the outcome and perhaps some pics or a video if I can get a spare set of hands to help


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