4age wont run right

[themaleman]

Hi, my 4age wont run properly. its from an ae92 levin. bigport redtop. in a suzuki. it starts but idles really high and when you open the throttle it almost dies before increasing the revs. we have tried using a timing light and also bridging t1 and e1 as this is meant to disable the auto advance while timing it. when we move the dizzy in the appropriate direction to adjust the timing the engine dies. the engine had been sitting for over 5 years in the shed. any advice would be greatly appreciated!

[Vertigo]

Sounds like you have no accel enrichment. Is it using a stock ECU? Fuelling ok?

[themaleman]

Ok bit of am update. Changed tps, map sensor, ecu, throtle, stil not runing right. Wiring is correct. The engine idles fine when map sensor is unpluged. And fuel presure is only 20psi at the rail. Nxt step wil be geting a new fuel pump 2morow morning.
Any thoughts on the map sensor?

[matt dunn]

20 psi rail pressure is not enough.

fix that first as it may be all the problem.

[KinLoud]

Yeah - from memory, problem could be related to throttle
Something like....
Throttle very slightly open because the little vacuum idle up thingy is pushing the throttle slightly off the stop...
The computer then ignores the jumper between t1 e1 and changes the timing so you can't set the dizzy properly

Push the throttle closed when engine is idling to see if it is fully closed.

Good luck

[Vertigo]

You should have at least 38psi, up to 48psi, depending on your ecu.

[themaleman]

thanks for the reply's. this is a strange 1! changed fuel pump and fiddled with tps dizzy to get it idling pretty good. also swapped the map sensor for a rectangle shape one (from my gtz). then all seemed fine. wasn't until we went to take it for a drive that it all turned to custard again. idle has gone out of wack and the revs still drop and the engine nearly dies when you give it throttle. im thinking maybe ecu so im going to look for another. we have 2 here to try from but they might both be buggered (unlikely i know but still possible). any other suggestions?

[Vertigo]

Check your fuel filter, pressure regulator (I have spares), anything that delivers fuel. Try some injector cleaner.

[themaleman]

pulled fpr off today and it looked nice and clean inside, both inline fuel filters are new, fuel lines are new and the new (2nd hand) pump still has its filter bag on it, injectors are pretty noisy so will try some injector clean. its strange to me how when you disconnect the map sensor the revs drop right down to was sounds like a normal idle. saying that we have tried 3 different map sensors and they all seem to do the same thing

[Stu-]

Have you checked to make sure there is a proper 5v feed and good earth to the map sensor?

[matt dunn]

maybe when you unplug the map sensor the car reads that as no vacuum and opens the injectors more to compensate for the fact you have no fuel pressure,

just because you unplug something and it gets better doesn't make it the fault.

Pressure regulators are pretty reliable ( as long as they are factory and standard)
so the easiest way to test for fuel is...


pull the return line off and run a hose into a bucket.
Start the car and if fuel comes out you have got enough pressure.
No fuel = not enough pressure

doesn't really matter about flow etc, it either comes out the return or it doesn't.

[themaleman]

The new pump is from a car that had a silvertop. We got 80psi at the pump from it. And also visualy saw the return line had heaps off fuel going back into the tank. Prety sure we checkd for 5v feed. Wil recheck tomorow. Dose the map sensor have an earth wire or relay on being bolted to the body? Thanks again for al the input!

[Vertigo]

That definitely sounds like a poked regulator to me.

[Stu-]

Yeah I agree that fuel pressure is way too low. Should be nearer 43pai.

Map sensor has three wires. Signal earth from ecu, 5v supply from ecu and signal return to ecu.

[themaleman]

thanks again for the replys, going to have another play around with the truck now. the new fuelpump we put in had 80psi at the pump. i will check to see what it is at the rail with and without the engine running. we have a spare fpr that is on the spare engine. i did take it off to try it but it was fulthy inside. like the previous owner ran it without any fuel filters. evan the mesh bag on the old fuel pump had been removed. will dunking it in turps be ok for the fpr??

[matt dunn]

80 psi at the pump? that must be with the lines blocked?

My next guess is that you have the supply and return lines around the wrong way.

[themaleman]

80psi was the presure gauge straight out of the tank. Just over 40 at the rail with no drop when it reves. Fuel lines are the corect way around. Taking it to get expert help this week. My guss is wiring or ecu. Wil post back with the problem(s) when found

[gepsk8]

How did u get on? Sounds like u need to set up timing again. Check cam timing.

[themaleman]

Hey, its runing great now, took it to Stu and he worked his magic. I think it was a combanation of faulty idle up vaulve, throtle body gasket, a couple of injector seals and wiring