16v won't fire up after inlet manifold swapping

[rado mc 0]

hi all,

 

i've a 1.8 16v 91 and recently swapped over my 42mm to a 50mm inlet manifold whilst my rado was off the road for a while, everything came off and went back togther ok surprisingly, however it plain refuses to fire up now?!

Checked for spark, got that and double checked all pipes and connections.

fuel is getting to the metering head as it sprayed out when i losened the main fuel in bolt and at the cold start valve. but it doesn't appear to be making it to the injectors. i've taken off the metering head and cleaned up the arm and so on so it moves ok. And also swapped the four fuel pipes and injectors with a spare set but still no joy :(

i found another thread (no fuel to injectors on 16v) which is very similar to my problem but it doesn't offer up a conclusion.

Do i need to take apart the metering head, do these things break or could it be something else really simple, cheap and easy (please).

 

thanks in advance

 

andy

[marty35 0]

i took mine off recently too clean it up,when i put it back together it would not start,it turned out that all it was that i had forgot to reconnect the vacuum pipe at the back of the mannifold .... hope this helps

[krnau 0]

42mm manifold has a vacuum pipe under the cold start injector, while 50mm one has it under the manifold (between cyls. 1 and 2)

[jamiehamy 0]

The mixture might be too lean now?

 

Could try this if you're clean and careful. Disconnect the metering head from the airbox and lift it up. Underneath, carefully feel for the arm. Push it up a small amount ( 1cm?). Hold it there and get someone to try start it.

 

If it starts, just let it go and carefully lower the metering head back down.

 

I had a similar problem with my 16v Golf and it was mixture related. I made it run a bit richer and it helped, although was not quite 100%.

 

Whilst this experiment might not solve the problem, it might at least prove it's capable of starting and hopefully help diagnose.

[Kevin Bacon 5]

Did you reconnect the cold start injector?

[Jim 2]

I'd be surprised if the 5th injector is to blame.. can normally start and run the car without it connected even in the coldest weather :|

[Kevin Bacon 5]

If the metering head fuelling is set correctly, then it will eventually start after a lengthy crank. With it connected, it should fire up immediately, which is why it's there.

 

Another reason why they can plum refuse to start is a jammed ISV. I used to carry a blunt object for whacking the ISV with during my 16v days as it happened so frequently.

[davidwort 0]

Don't take the metering head apart.

Try turning the ignition on and off several times, allowing the pump to prime the system but not all the way so you crank the engine. If the whole system was drained it can take a while to get the air out on cranking and to pressurise the system back up again.

To check the plunger on the metering head, crank the engine for 10 secs or so to pressurise the system then lift the airflow plate, should have even resistance all the way up but no resitance when moved down quickly.

 

If you have a vacuum or engine breather system leak (or pipe not connected) it will fire but die, so re-check all the hoses and pipes.

If you disconnect the coil from the dizzy and crank the engine or jump the fuel pump relay socket main pins (use the battery negative lead to turn the power on/off) and lift or wedge the metering flap up, you should get fuel sprayed from the injectors, you could pop one out into a bottle to check, or just look in through a sparkplug hole, should smell it anyway.

[rado mc 0]

cheers guys,

 

i'm gonna have a double check on that different positioning and connection of the vacuum pipe, i've have been away for a few days and not had chance to have a real go at anything yet just oked my nose under and scratched head not wanting to be splattered with fuel again.

The cold start injector is definately in place, i even losened that when originally looking to see what had fuel and didn't and it soon squirted out on half a turn.

Is the ISV the idle stablisation valve? if so thats buzzing away quite nicely so i'm ure thats fine, but i'll give it a crack anyway for good measure.

i'll wait till i 've got a mate over too so i can try the raising the arm and cranking advice and hopefully have some firing which will spur us on.

 

I have primed the pump on and off without actually going for ignition and after the 2nd or 3rd go the note of the pump changes a little like its slowing or struggling. but fuel shoots out of the metering head when the main fuel line bolt heads are slackened afterwards so i presumed the pumps ok?

 

will post again as soon as any news

 

thanks again!

[kerrly 0]

so how long was the car off the road? if you prime the pump a few times and it starts sounding lazy it makes me think your battery has had it.

 

try a different battery, you really need min of 12v to fire the engine

[rado mc 0]

Right thats xmas, new year out the way etc!

Sorry for the delay.

 

Regarding the battery its been off the road for a while now, but is garaged, i'd taken the battery out and always had it charged plus its relatively new, cranks away no problem so i'm sure it isn't that.

 

However I did get a chance to take the metering head off as suggested and the arm did have consistent resistence as mentioned, so I was happy with that.

I wedged a rag just under it so it was up about a cm and as soon as I turn the ignition I could clearly hear the fuel eventually gurgling on its way to the injectors. Cranked it and sure enough it fired, but straight to 3-4k rpm. oops!

Soon figured that the less raised the arm was in the metering head the less it revved. However in more lower idling speeds its sounded dog rough with a lot of juddering and the gas pedal made no difference in revving speeds. the only thing that altered the revving was that arm. I let it run for a few mins, then turned it off and put it back together but it didn't work. Only seems to fire when that arm is about half a centimeter raised and cuts out when it drops to its normal starting point and thats pretty much as far as I have got with it being this time of year and winter etc.

 

so in a nutshell, fires up ok, idles awful, can only alter rev's with that metering head arm. :brickwall:

[jamiehamy 0]

hmmm, it'll only rev with the metering arm? What happens when you get a steay lowish revs with the arm, then use the throttle to hold the revs up, letting the arm do it's own thing?

 

I'm convinced this is an isv issue as it's virtually identical to the issues i had with my MK2. The ISV didn't buzz tho traced it to a broken wire which cured all woes with a quick solder. Possibly the ISV control unit, which on the MK2 sits under the centre console in front of the gearstick - isv might buzz, but wrong signals being sent?

[boost monkey 0]

an ISV wouldn't stop a car revving. My ISV has always been dodgy but I can still rev the engine.

[krnau 0]

an ISV wouldn't stop a car revving. My ISV has always been dodgy but I can still rev the engine.

and it would even fire up by pushing the accelerator

[rado mc 0]

when i get the revs close to idling speed using the arm it struggles not to cut out, so naturally reaching for the throttle and twisting it never made a difference.

Would i be wrong in searching parts for another metering head/airbox etc?

its prob gonna be a few more weeks until i get time again to have another good look and its a bit lighter in the evenings, makes it worse when i saw mint burgundy VR6 cruise past my work place today :(SP_A2930.jpg[/attachment:1oltqgcg]