bad timing on rb?

Website · Post by **frosted flakes** » Sat Dec 06, 2003 6:19 pm

Hello,

Whenever i shut down my engine and pull out the key my engine turns back on for about half a second then turns off. Why does it do this? Is this bad timing? Also i am having hard starts in cold weather. Once i make that morning start it seems good all day. Does this have to do with timing?

Tony

Post by **Wulfgang** » Sat Dec 06, 2003 6:19 pm

There is an air regulator - not the AAC - that should be connected to come on when your fuel pump comes on (it should connect to your fuel pump relay). Is it working? It is a temperature sensitive switch and could cause hard starts.

Also, as far as your engine running after you stop it... are you describing run-on (or "dieseling" as some people say)? If so, your engine keeps running because of hot spots in the cylinders. This could be caused by running lean (a vacuum leak maybe?). If you are describing something else, like your engine actually stops and then turns back on... must be electrical.

Shane

Post by **wga240** » Sat Dec 06, 2003 6:19 pm

Could you elaborate a bit more on this air regulator? The fuel pump gets its signal directly from the ECU, unlike when the KA was in there. So, is there even a functioning fuel pump relay in the system now?

I too am having cold start troubles, and I definitely didn't wire up an air regulator to the fuel pump relay.

Post by **Wulfgang** » Sat Dec 06, 2003 6:19 pm

Whoa... why does your fuel pump get a signal "directly" from the ECU now? All of the wiring diagrams I have seen show that the ECU (pin 18) grounds the fuel pump relay (to turn it on) just like with the KA. Even if you have a GTR with a special fuel pump control unit, the pump should still be powered via the fuel pump relay.

I have seen an air regulator on some of the RB20DET wiring diagrams. It is wired in parallel with the fuel pump, coming off of the fuel pump relay. Interestingly enough, it is not on the engine harness wiring diagram I have, but it IS on the general wiring schematic. So where is it located? I don't know. (Just like that little silver box on the passenger side of the engine bay... nowhere to be seen on the wiring diagrams, but it is clearly part of the engine harness.)

IIRC, the KA has an air regulator that opens when energized, but since it is made of bimetal, it closes after it heats up. So this would open when your engine is cold, letting a bit more air in to start it up, but it will close after your engine is warm, even if it is still energized. Perhaps the RB has the same mechanism.

When (if) you find it, let us know where it is. I just started working on my wiring, so it will be a while before I can get to that.

Shane

Post by **PROJECTRB240SX** » Sat Dec 06, 2003 6:19 pm

THE FUEL PUMP PIN ON THE ECU SHOULD BE WIRED INTO THE FUEL PUMP RELAY ON THE CHASSIS HARNESS IN THE CAR. AS FOR START UP AFTER KEY REMOVAL, IT SURE SOUNDS LIKE GREMLINS.... COULD BE A BAD INGITION WIRE CONNECTIONS, CROSSED WIRES, ETC.

Website · Post by **frosted flakes** » Sat Dec 06, 2003 6:19 pm

No no no your are misunderstanding my problem everyone. Its not anything electrical. and ONLY happens when the engine is cold. Once i start it up the first time of the day it does good all day. I am almost positive it has to do with the Cam angle sensor being off. I just need to adjust it. I have been talking to someone and they had success buy adjusting this cam angle sensor. This also solves the "diesel" problem i am having.

Post by **Wulfgang** » Sat Dec 06, 2003 6:19 pm

Ok, I just checked the diagram again. The air regulator is on the engine harness diagram after all. And it is wired to the fuel pump relay output, as I mentioned before.

Now I think I remember seeing where the air regulator was. If you look into the rats nest of vacuum lines, fuel lines, and injetor wiring, up inside the curve made by the intake runners, you should see the air regulator near the #3 and #4 cylinder intake runners. It is a ~3" metal tube with a hose connected to one end and a square box on the other end. The wire you need to connect should come out of one of the plugs on the harness and the color should be B/Y (don't quote me on the color... verify it with a multimeter).

IIRC, it looks just like the KA air regulator and is mounted in almost the same spot on the runners (KA24DE).

Shane

Website · Post by **frosted flakes** » Sat Dec 06, 2003 6:19 pm

OMG you are so right actually. There is a skinny black hose that is connected to this small black box with a plug that looks like it would go into it. Is this what it was. That was one of the only things we had that wasnt connected to anything. Ill try get pictures later this afternoon.

Post by **JonPowell** » Sat Dec 06, 2003 6:19 pm

The small black box that you are talking about, is it coming off the intake plenum, if so that is the sensor for the factory boost gauge.

3 wires?

Post by **PROJECTRB240SX** » Sat Dec 06, 2003 6:19 pm

YEAH THATS THE BOOST GAUGE SENSOR, BUT IF IT IS NOT CONNECTED OR BLOCKED OFF YOU WILL HAVE A MANIFOLD LEAK CREATING A HARD-START.

Post by **tyler03** » Sat Dec 06, 2003 6:19 pm

frosted flakes, i think it might be a rb20 thing. I have the exact same problem you do. In the mournings when i go to start my car i have to turn it over 5-6 times sometimes more before i can get it going stong. But after that, its good to go all day.

Post by **Wulfgang** » Sat Dec 06, 2003 6:19 pm

Also sounds like the boost sensor unit (which you don't need). The air regulator is mounted on the intake manifold, not the firewall. The unit is square with a long metal snout looking thing. The vacuum hose connects to the snout. Look for it by the injector plugs.

Post by **tyler03** » Sat Dec 06, 2003 6:19 pm

Are you talking about that little nipple looking thing on the passenger side, on the intake manifold? I have my boostgauge line hooked up to that, is that wrong?

Post by **PROJECTRB240SX** » Sat Dec 06, 2003 6:19 pm

NO THAT IS WHAT IT IS FOR.... BUT TECHNICALLY YOU ARE NOT GETTING A TURBO BOOST READING YOU ARE GETTING A MANIFOLD PRESSURE READING.

Post by **tyler03** » Sat Dec 06, 2003 6:19 pm

so should i put the line somewhere else?

Post by **NISMO_RB25** » Sat Dec 06, 2003 6:19 pm

doh.. I didn't even thing to run the boost gauge off of that. I just T'd into the one going to the BOV.

Post by **PROJECTRB240SX** » Sat Dec 06, 2003 6:19 pm

MANIFOLD FOR FINAL BOOST PRESSURE, BOV LINE FOR ACTUAL TURBO PRESSURE.

Post by **wga240** » Sat Dec 06, 2003 6:19 pm

Wulfgang wrote:Whoa... why does your fuel pump get a signal "directly" from the ECU now? All of the wiring diagrams I have seen show that the ECU (pin 18) grounds the fuel pump relay (to turn it on) just like with the KA. Even if you have a GTR with a special fuel pump control unit, the pump should still be powered via the fuel pump relay.

Wow, sorry about that. I was half awake this morning when I posted that and looking back on it now it makes absolutely no sense

Thanks for the help with this air regulator. I'm gonna go see if I can locate what you're describing.

Post by **Wulfgang** » Sat Dec 06, 2003 6:19 pm

This is the air regulator on the RB20DET.

You need to find the B/Y wire going to the Q plug that was on your engine harness under the dash and connect it to your fuel pump relay output. On the S14, this is pin 10 on the F3 plug, also B/Y.

My FSM says pin 26, just to give you some idea of how screwed up the S14 FSM wiring diagrams are.

Hope that helps.

Shane

Website · Post by **frosted flakes** » Sat Dec 06, 2003 6:19 pm

wow thanks a bunch! Im gunna go check that out tommarrow!

Post by **wga240** » Sat Dec 06, 2003 6:19 pm

Wulfgang, you are the man! I'm also gonna try and wire this up tomorrow

Post by **wga240** » Sat Dec 06, 2003 6:19 pm

Just to let you guys know I wired this up and it made no noticeable difference in starting. Oh well. Back to the drawing board.

Post by **Wulfgang** » Sat Dec 06, 2003 6:19 pm

Ah bad luck! Ok, that was really the only idea I had. Not sure what else could cause hard starts... Maybe the air regulator is sticking?

Can you hear your fuel pump start if you just turn your ignition to ON and don't start the engine? You should hear it run for maybe 2-3 seconds.

Shane

Post by **wga240** » Sat Dec 06, 2003 6:19 pm

Yeah I can hear my fuel pump. I even got got a multimeter and put it on the fuel pump relay output wire. For the 2-3 seconds the fuel pump is running, that wire has power. After that it doesn't. Is the air regulator only open when it has power? If so then the way I wired it, it appears it would only open for a few seconds.

bad timing on rb?

bad timing on rb?

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