fresh swapped blacktop sr won't stay running

[josho]

I bought a complete blacktop sr20det from a buddy of mine 2 weeks ago. He pulled it straight out of his car and the next day it went into mine. When he pull it, it was a perfect running motor! I put it in my car and it ran fin the first day. I was still running the factory fuel pump so I swapped in a 255 and also relocated the battery. Now the car will not stay running. It will crank and start everytime, but will die 2-6 seconds afterwards.. I have checked the alt fuse, vac lines, maf, cas, ignitor chip, new plugs, and I have hardwired the fuel pump so I know it's getting fuel. After all that, it's still doing the same thing. Any suggestions?

[josho]

also, my battery light and brake light is on.

[Sugar]

You moved the battery, and now it won't stay running... Check the connections, check the ground. What gauge wire did you relocate it with, make sure its getting all it needs.

[Blown240sx]

If the battery and brake light are on then you have a voltage problem. What gauge wire did you use on the relocation? Did you ground the battery well? Did you ground the motor to the chassy?

[josho]

it was acting up before I did the relocation. Before then I just had jumper cables from a battery to the terminals. Now when I took it for a spin the first time, I unhooked the battery and it killed my alt. ( I know, that was stupid). But even after that, it would crank right up with the cables hooked up. But the next day it wouldn't. So now I'm lost. Do you think it could be a bad alt.?

[Sugar]

Go test it.

[OM3GA]

definitely test your alternator, that sounds like its the problem 100% Also check your battery, that is not something to have bad connections on. A lot of people relocate without doing it properly. Not saying that is you but just re-check it.

[josho]

I tested the alt and it said 14.5 volts so it's good. And the battery is relocated the same exact way that my silvia battery is relocated. The only new thing I have found out is that the car runs the same way with the iac plugged in or not... But if the iac was bad, wouldn't it just idle funny? I got it to crank today. I could rev it up but it wasn't doing very well. It sounds like it's out of time... But it's not. Any other suggestions?

[OM3GA]

maybe a coil pack is bad? Like #1

[josho]

I hate shooting down your options but, I swapped the coilpacks from the silvia into the blacktop and stil nothin happened. I believe I have literaly tried everything. I almost just want to let it sit and finish up on the silvia.. But at the same time, I need to finish this car so I can have a DD.

[Sugar]

Start by pulling any codes. Then check for spark/fuel and timing.

[josho]

I was messing with the car last night and found out a few more things that could help figure this out. I pulled the spark plugs and they were black and smelled very strongly of gas.. They are new plugs. I cleaned them and tried to crank it a few more times, with the clean plugs re-installed. Pulled the plugs again and they looked the same. Also when I pull the dip stick it smells like gas.. Maybe leaky injectors?

[Sugar]

Well yes, definitely a fuel injector issue. Check your fuel pressure, could be injectors or a FPR. Change your oil before you continue, gas an oil do not make for healthy rod bearings.


I had oil that smelled of gas just after a swap. It turned out to be the combination of a fuel pressure regulator and a 02 sensor that was wired incorrectly.

[josho]

ok thanks. I have my silvia for parts right now so maybe all find the problem and have what I need. I'll start by swapping out the fuel rail and injectors.

[josho]

Ok, so I sanded down all the grounds, cleaned the plugs and started up the car; it ran a lot better! I noticed that a plug wasn't connected so I connected them and the car fell on it's face and cut off. I'm not sure what the plug is but it's right beside the throttle body, it had two other plugs that come off of it (one is like a wire connector and the other one is red, sorta looks the the maf plug). So I swapped it out with the one off my silvia and it started up great! It would hesitate a little when reving but would clear up and rev fine past 1500 rpms. So I went to test drive it.... As soon as I tried to give it some gas it wouldn't do anything. It would just hesitate and the rpms wouldn't move. Sound like timing to anybody?

[PyR0NiAk]

Definitely does sound like timing. Have you done a compression test?

[josho]

I sure haven't. The motor was just completely rebuilt about 2000 miles ago. But I'll do a compression test and see what comes up.

[josho]

what are some symptoms of a bad cas? Does this sound like it could be the problem? How can I csn to make sure??

[Sugar]

CAS sends signals to fire spark and fuel, so it could be an issue depending on how "failed" it is. Even if they check out they can still have issues. Try swapping it out with a known working one, make sure you line it up right.

[josho]

well I finally pulled codes.... Got the 55. So does that basically rule out any electrical issues?

[Sugar]

Generally, but I had a faulty maf that worked fine, it just read high voltages/rpm. My friend had a CAS that only gave him issues after 5500rpm.

[josho]

Generally, but I had a faulty maf that worked fine, it just read high voltages/rpm. My friend had a CAS that only gave him issues after 5500rpm.

Good news!!! I swapped the blacktop into my silvia... and it runs!!! So the problem is either wiring harness or the body harness. Whats the best way to go about checking either harness?

[USMCgetsome]

i'd say engine harness check to make sure your 12vdc switched and grounds are installed properly.