Weirdest problem ever....

[ncturbospecv]

In the process of finishing up my rb25 swap into my s13. Car was running fine last week. I go to start it and take it around the block after installing my new sparco seat and as soon as i back it out of the garage it shuts off. It sounds like the car is running out of gas. It's got plenty of gas(3/4 tank), new walbro pump, and new fuel filter. Now here's the weird parts... The car will run when any of the back part of the car is jacked up. Runs fine, revs fine, but as soon as you put it back on the ground it acts again like its running out of gas and shuts off. I checked under the car for any kinks/pinched fuel lines (stock lines) and they're all fine. Yes the lines are routed correctly and not on backwards. I even borrowed my friends walbro pump out of his sr car and same thing. If anyone has any suggestions it's greatly appreciated. i'm completely lost.

[TheRBguy]

Make sure your tank is clean and not clogging s*** up and is your fuel filter clean?

[ncturbospecv]

The sock on the filter is clean and the z32 filter is new as well. Is there any way the ecu coolant temp sensor could have any affect on this? I just replaced it and thats the only thing i even touched motor wise in awhile.

[WithHonor037]

When the car is set down all your suspension is under load and causes a natural squat. I might guess that a breather hose or fuel line that isn't pinched when jacked up might be getting pinched when the car is lowered down. See if there is anything routed near your rear suspension that could be getting pinched when the car is on the ground.

[ncturbospecv]

thats what i was thinking but i've jacked up the car and looked. Nothing's routed near any suspension pieces that move. I even jacked up both sides of the suspension to see if anything gets pinched while the suspension is compressed and didnt see anything.

[WithHonor037]

Im assuming that you can hear the fuel pump running when the car is level and the key is in the on position? Pull the fuel feed line and put it in an empty water jug. Turn the key on to make sure your fuel is making it to the rail from the tank. If it makes it that far I you can pretty much assume the problem lies in the engine bay.

[ncturbospecv]

today i actually pulled off the return line at the tank and tested it and fuel is flowing all the way back to the tank.

[WithHonor037]

Is everything grounded properly. The problem could actually be electrical. An unstable ground could cause poor injector response, (dk if rb's use a distrubutor) could affect spark and timing quality. That would be the next thing I looked for.

[ncturbospecv]

ive checked all the grounds that i know of and they're all still nice and secure. I made sure to double check the ones closest to the temp sensor from when i was installing it. I might have over looked something and will check again.

[WithHonor037]

Good luck man. Its gotta be something to do with the air/fuel/spark I would think. And you have fuel so that narrows it down to two.

[ncturbospecv]

yeah thanks for the imput. this car has been a fight the whole time. Just had it running good too. Im wondering if its got anything to do with this new ecu water temp sensor i put in. Its the only thing i've changed on the motor besides finally putting the rest of the exhaust on.

[USMCgetsome]

sounds like you need to check your cas and spin it to see if your injectors are firing. Hell pull the fuel rail and crank the car see if they spray fuel. Afterward i'd say check your maf.

[ncturbospecv]

The cas works and the injectors spray fine. The car runs perfectly fine when the car is jacked up in the back.

[jey_253]

Does the fuel pressure change with the car jacked up vs sitting level?

[ncturbospecv]

I dont have a gauge hooked up now. Im going to have one hooked up this weekend to check it.

[ItzGenX]

You can rule out suspension load and squat by having the rear and front jacked up level to get all the wheels off the ground. If it doesn't run like that, then you have something else being effected by gravity. Weak sticking relay perhaps? Puddled water running around somewhere hidden? Loose wire shifting around? Weak fuel pump? Fuel float doing something trippy? Bad fuel settled to the bottom of the tank and tilting makes it move away from sock? (water sinks in gas)

In "pain in the a**" mode, I say check fuel pressure (with fresh fuel) and turn CAS manually with exposed coil/plugs (in vertical position) and fuel rail to see if all injectors and coils are firing (away from each other of course, don't start a fire). This way you can find things to scratch off the list.

Oh, and please do not try catching gasoline in a 'water jug' or non-chemical resistant plastics for very long. Gas can/will melt weak and soft plastics.

[WithHonor037]

Yea that is a good point but I never meant to imply storing gasoline in water jugs. Simply catching it in there and sitting it a few minutes is far from adequate time for the gasoline to erode your average water jug. I guess I shouldve specified that. Good catch.

[ncturbospecv]

Thanks for the suggestions guys. I dont have time to work on the car till friday. I'll try everything suggested and get back to let you know if i find anything.

[ncturbospecv]

Ok just went to hardwire the pump with a relay and now the pump wont come on. The fuse is fine. Can someone verify this is right? This is the diagram i used...

85: Blue/red from plug
86: chassis ground.
30: Battery
87: Blue/red from pump
Also grounded the white/purple from the pump to the same ground as the relay.

[turbotank]

The sock on the filter is clean and the z32 filter is new as well. Is there any way the ecu coolant temp sensor could have any affect on this? I just replaced it and thats the only thing i even touched motor wise in awhile.

the ECU coolant temp sensor 100% has an effect on your car not starting... i had a bad coolant temp sensor on my car and what would happen is the car would start but then just shut off.. whats happening is your ecu thinks the car is running SOOO cold or SOOO hot i think it defaults to cold tho but anyways when my car started the ecu was litterally flooding out the spark plugs with fuel trying to compensate for the "false temp" the sensor was sending it, so what i had to do was clean of the spark plugs wait a while for everything to dry re install them and the same thing happened i started the car it started right up but then shut off after idling badly... soo i replaced the coolant temp sensor off of a hunch and cleaned the spark plugs once more and car started first time with no problems since! hope this helps man!

Tony

[WithHonor037]

That makes alot of sense but I cant understand why the rear end of the car being jacked up would have any effect on the coolant temp sensor.

[ncturbospecv]

The sock on the filter is clean and the z32 filter is new as well. Is there any way the ecu coolant temp sensor could have any affect on this? I just replaced it and thats the only thing i even touched motor wise in awhile.

the ECU coolant temp sensor 100% has an effect on your car not starting... i had a bad coolant temp sensor on my car and what would happen is the car would start but then just shut off.. whats happening is your ecu thinks the car is running SOOO cold or SOOO hot i think it defaults to cold tho but anyways when my car started the ecu was litterally flooding out the spark plugs with fuel trying to compensate for the "false temp" the sensor was sending it, so what i had to do was clean of the spark plugs wait a while for everything to dry re install them and the same thing happened i started the car it started right up but then shut off after idling badly... soo i replaced the coolant temp sensor off of a hunch and cleaned the spark plugs once more and car started first time with no problems since! hope this helps man!

Tony

Thanks a lot. I figured it had to be the temp sensor because thats the only thing i've replaced/touched on the car. I have an oem nissan one comming tomorrow to try. Its doing exactly what you say and if i let it sit for a min to "cool off" it will start back up again for a little bit then shut off. I'll try the new temp sensor tomorrow and post. Thanks again!

[turbotank]

No problem buddy! it was honestly the weirdest problem ive ever had with a vehicle! it through me for a loop for a while! glad to help! hope its definiently your problem!

[ItzGenX]

Couldn't you just unplug the coolant sensor to rule it out like a bad MAF? A bad one still plugged in gives the ecu wrong resistance readings which throw it off, but if you unplug it, there is no resistance at all. Unplugging it will just let the ecu that it's not plugged in for a limp/safe/open loop mode, and it will go into preprogrammed map with a preset flat fuel correction table. I also don't see how jacking up the rear would affect the sensor unless there's an air bubble trapped right at the sensor, but the air should be the same temp as the water around it if the engine is off and rested for a long period of time.

[turbotank]

no if the sensor goes bad it goes to a default open which would be the exact same thing as not plugging the sensor in... so whether or not the sensor is bad or you have the sensor unplugged you will have the exact same problem.. i know this for a fact becauase i tried unplugging it and same prob was happening so i did research into the sensor and its exactly what i said there is no limp/safe/open loop mode in the ecu if the sensor is reading open its just telling the ecu that its fubared

it could have something to do with the sensor being twerked around with the coolant or flex when the car is on jacks or something electrical parts are very touchy im an electrician for the F-15E in the air force .. what a PITA lol

[ncturbospecv]

ok guys got it working amazing now. It wasnt the coolant sensor at all. It has something to do with my wideband. I just started unplugging all the electronics i've added to the car (just gauges and an safc) and found out its got something to do with my wideband. I've moved the ground around and still the car acts up. Im maybe thinking its got to do with whatever power supply i have it tapped into at the moment. But in the mean time the car drives good and the screamer dump pipe sounds awesome!

[WithHonor037]

Glad to hear you got it all sorted out.