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Discussion Starter #1
Hey guys, I really need some help. I bought a rebuilt sr20det and swapped it into my 89 240sx. I am ripping my hair out trying to figure out what my problem is. The motor will crank and crank and sounds like it is almost to the point of starting but it doesn't. Ive physically pulled the fuel rail to see if the injectors are firing and all 4 are, and not leaking. I also pulled all the plugs and all 4 are getting spark. When cranking the motor will sometimes give out a really really loud pop. Also black smoke will come out of the exhaust when cranking. I've also tried squirting starter fluid in but it ignites in the intake manifold and pops loud... Also the plugs are wet when pulled after cranking.
Troubleshooting I have done.
  • New Fpr
  • New spark plugs
  • Unplugged maf and cranked no difference
  • New ignition chip
  • New 02 sensor
  • All fuses in engine bay are good
  • Checked all grounds
  • Put cas in 180 out just to see and no difference
  • Prob some other stuff I'm missing​
I really would appreciate any help you guys can give me it's been weeks and I just want to drive it. Thanks.
 

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WHP11 CVT M6
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135 Posts
you said it was rebuilt

by whom and to what specifications? cams, compression, headwork?

the first thing to check would be the cam timing, you must verify this. doing a compression test can also indicate if the cam timing is incorrect without being invasive, although the engine would be cold, just hold the throttle full open and within 5 rotations of the engine u should have a decent reading if all is well.

what ecu? is it known good ecu?

I expect the fuel pressure would be ok if you say the injectors are spraying properly, it should at least start and idle if even it idles poorly.
 

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Discussion Starter #5
you said it was rebuilt

by whom and to what specifications? cams, compression, headwork?

the first thing to check would be the cam timing, you must verify this. doing a compression test can also indicate if the cam timing is incorrect without being invasive, although the engine would be cold, just hold the throttle full open and within 5 rotations of the engine u should have a decent reading if all is well.

what ecu? is it known good ecu?

I expect the fuel pressure would be ok if you say the injectors are spraying properly, it should at least start and idle if even it idles poorly.
I've done some poking around and I pulled my fuel rail with the injectors still attached and cranked to see how they fire. When I did this they all fire at the same time? Is that supposed to happen? I feel like it would flood it am I wrong? Also cam timing is good it had been tripple checked 4 times and I have good compression also. The ECU was working right before I got it.
 

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WHP11 CVT M6
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135 Posts
when cranking the injectors fire concurrently, after the engine starts, it fires sequentially, if you disconnect the start signal from the ecu when cranking, you should be able to see sequential injection.

If all the things you say are ok are actually ok then you should be good to go. Only one more thing I can think of and that is to get a consult 1 software connected and look at any error codes and the live data with ign on and while cranking, something may turn up that is not obvious otherwise.

if you think the injection or injectors on the whole are the culprit. disconnect all injectors, pull fuel pump fuse. get someone to inject propane into the intake with a propane torch or the end of a hose from the grill or something like that(u will need an adjustable regulator or some way to pinch the hose to control flow with the grill hose), crank and see what happens.

if you have enough propane the engine will start and idle, too much or too little and it will do nothing.
 

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Discussion Starter #7
when cranking the injectors fire concurrently, after the engine starts, it fires sequentially, if you disconnect the start signal from the ecu when cranking, you should be able to see sequential injection.

If all the things you say are ok are actually ok then you should be good to go. Only one more thing I can think of and that is to get a consult 1 software connected and look at any error codes and the live data with ign on and while cranking, something may turn up that is not obvious otherwise.

if you think the injection or injectors on the whole are the culprit. disconnect all injectors, pull fuel pump fuse. get someone to inject propane into the intake with a propane torch or the end of a hose from the grill or something like that(u will need an adjustable regulator or some way to pinch the hose to control flow with the grill hose), crank and see what happens.

if you have enough propane the engine will start and idle, too much or too little and it will do nothing.
Okay, thank you so much for the help. I've heard of the consult port and I've looked around to how to go about that and I can't really find a straight answer. Can you inform me on that? Like where do I wire it in and where is the best place to get one of them?
 

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get one from the wreckers off another vehicle - it's normally the only way.

the pins you need to connect are normally the 4 around the centre bolt -RX/TX/CLK/CHK + plus ignition switched power and ground (which you could get from the ECU power supply (pin 38/39) but normally advised to get something on a different circuit so you dont take out the ECU if you trip the fuse on anything connected.

 
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