unreliable ignition

[Jmac]

Yes now that you have given more info sounds like the fuel pressure is leaking back on shut down mate. Try changing your fuel non return valve which is on the end of you fuel pump, im sure if you had a fuel pressure gauge on there , you would have no holding pressure, these non return valves are common on these mate. Turning over so much is you building up pressure again, and of course if you have low battery and bad earths they all add up to a poor starti g vehicle.

[86gti]

Heya.
Had this problem with my K-jet a cupla years ago......
Best thing to do is get a fuel pressure guage and run a few tests...
Mine turned out to be a faulty Main pump...
started fine when it was cold, but got jerky when it warmed up, also didnt want to start when it was warm.
......
the relay wont turn the pumps on untill RPM is registered...so turning ign on and off shouldnt Purge nor help at all, neither will pumping the accelerator unless a car has a carburettor..............

Also had the problem of poor starting not long ago, wind over fine some days, slow other days......was the connection to the starter motor..
got loose and daggy...made new leads up and now its all fine...

but if its the pumps etc???? Here is a part of a Kjet over view ive written up elsewhere.

PUMPS.....
Pick up Pump, Lift pump, transfer pump or what ever you wish to call it is the first pump to pick up the fuel in the tank.
Make shure this is working well...If this doesn't work well it will starve the Main pump and you will find yourself replacing 2 Pumps!!
(been there done that)

Testing this pump is fairly simple.
Find your Fuel pump relay.... This was no where near where it said it was in the bently manual so im guessing the US versions differ a bit from the European vehicles. My relay was stamped number "62" and was in the top row of relays on the left.
when you get it out you will see 2 large pins and 2 or 3 small pins (cant remember how many small ones..but they dont matter at this stage)
where the 2 lage pins fit into the relay holder is where we are looking
Grab a switch (toggle ones are best - 2 pole) solder wires to the poles and fit large spade bits on the end of the wires.
make shure the switch is off and plug the spades into the 2 LARGE slots in the relay holder.
dont turn it on yet!!!!!!(if its not off you will hear the pumps fire up when you plug it in, no harm done, just turn it off quick)
have a look under the car driver side just under where the back seat is....
you will see the main pump with a plug going into the top of it. It a std type plug that can be removed by pushing the wire clip at the top and sliding it off.
once you have done that we will find the Lift pump.
take up the carpet in the boot well. to the right and up a little from the spare wheel well you will see a plate with 3 screws in it.
undo them and take the plate off to reveal the top of the pump and Fuel guage sender.you will see 2 hoses, both with arrows.
one points in (returned fuel from system) one pointing out...one pointing out is the one you want...
Take the hose off it, and find another bit of hose that will fit over the outlet.
now we are ready to testthe delivery rate. Grab a mesuring cup that will hold at least 500cc and get ready to let the fuel go into it.
get some one on the switch ( ill do it for a tinnie or 2)...
flick the switch and leave on for 10 seconds
you should get at least 400cc / 13 and a half Oz. into the cup...
If you have..thats good news..if not......................
Replace it before the main pump decides to retire.
Try to use Genuine Bosch parts where ever you can . I am running a high pressure Carter Pump in mine and it seems to work fine although a bit more noise than the Bosch product.


.......................
then ontooooooooooooooo

Main Pump

In the MK2, the main pump is located in the smaller tank (reservoir)....
This pump is a roller cell pump, with the fuel entering the pump and being compressed by rotating cells that force it through the pump at high pressure. It will apparently pump upto 8 bar (120 psi) with a delivery rate around 4 to 5 litres per minute .....the system relies on pressure to run well....so this is one of the Main parts of the system.
Within the pump is a pressure relief valve that lifts off its seat at about 8 bar to stop the pressure incase the filter, fuel lines or other things become obstructed. The other end of the pump (out) is where the non-return valve is.... When the voltage to the pump is removed it closes the return and maintains pressure within the system... we get to that later
The operating pressure in the system is approximately 5 bar (75 psi) and at this pressure the current drawn on the pump is around 5 to 8 amps.
Apparently the inside of the pump (armature) will spark etc......!!!! sounds bad when fuel is passing in there...
But absence of Oxygen means no explosion! hahahaha....

To test your deliver rate of the main pump get under the bonnet and find the fuel return hose....
this hose returnes the fuel back to the tank that has been unused.
the K-jet system doesn't Pulse fuel into the manifold like an EFI set up....it is always injecting so there is always fuel being recurculated..
plug the main pump back in where you unpluged it to test the lift pump.......
the return line on mk2 is just infront of the firewall on the driver side (aus)...

this test also relies on the voltage at the main pump..so low voltage at the pump means a bit less delivery...
Ive got a chart here that is measured in cm3.... i dont recall what it translated to in OZ or cc...but look up a conversion chart to translate
see what sort of voltage you have at the pump between 10-12v is usuall...

now run the return line into a measuring cup (mid sized) from memory mine held about 17oz.
run the pumps from the switch for 30 sec and turn off.

at 10v you should have around 350-380cm3
at 11v you should have around 500-520cm3
at 12v you should have around 650-670cm3

Ill edit this later and give you measurements that make more sence..lol.

this is where i found a problem with my MK2 a while ago.
all my pressure tests were fine, but my delivery from the main pump was less than half what it should have been...
was hard to start when warm, would miss and carry on allot, and eventualy wouldnt start at all...
new pump had it running better than ever

If you plan on getting more indepth than this i would urge you to get a bently manual... (I got mine from Pitstop book shop in WA)

................
thats just some info from my daily diray. lol
give it a go, hope this helps u out.....

My pressure to the fuel dizzy was ok, but the flow rate was shocking........
i have both pumps instock if you need any...

[Jmac]

Just on that one remember the non return valve is on the pump and you may be throwing the pump away when the valve may be the drama. Good bit of info there

[Golf Loon]

Nice info, but it still pulses the pump if you turn the ignition on and dont start the car.

[86gti]

Just on that one remember the non return valve is on the pump and you may be throwing the pump away when the valve may be the drama. Good bit of info there

for shure Jimmy,
like i say, test all the pressures first...never replace things till you know for shure. lol...or it could end up being expensive.

[86gti]

Nice info, but it still pulses the pump if you turn the ignition on and dont start the car.

Unshure about all systems, but 3 kjet cars ive worked on have no power out of relay or into pump at any stage of ignition being turned on unless its being cranked...may differ on some set ups.

Here is a lil more info on the relay and accumulator etc.......

PUMP RELAY

Tachometric relay...... what that means is it only responds and sends a voltage to the pump when the engine is turning over or actually running. The relay gets its signal from the negative terminal of the coil , this confirms that the engine is turning.
this rely is kind of a safety device... if the vehicle is involved in an accident when there is a possibility of a fuel line being fractured, the engine will stop due to a lack of fuel, the signal from the coil stops and then there is no voltage at the pumps.

if the car wont run, get someone to see if they can hear the pumps going while its turning over....

My relay was a bit of a bugger to find....my bentley manual said it was somewhere that it wasn't.
on my mk2 (UK) it was relay "62" as posted before.

as explaned previously bridge the 2 main pins on the relay with a switch, and a 10 amp fuse in the line too...just to be safe..
flick it on and see if it goes.lol.....
I've had a weird problem with mine of late...I park on a hill at work, and a couple of times ive just gone to roll start it..
it wont go, and then it will turn over but the pumps dont go..so i bridge the pump relay and start it, turn it off, then put relay back in and it goes....
so i havn't tried to run start for a while....might be the relay, and maybe i should change it..



FUEL ACCUMULATOR
(next to the main pump on a mk2)

It accumulates fuel......lol.
and it's the first part in the fuel system after the pump.
Its first job is to help smooth out any pulses in the flow of the fuel, this is achieved by passing the fuel through a series of baffles and into a chamber giving it smoth flow. Its other role is to maintain pressure within the system when the fuel pump has been switched off.
This is achieved by the accumulator spring and diaphragm pushing against the fuel.
When engine is running the diaphragm will be against its stop within the spring's chamber. When the engine is stopped and the non return valves close the spring pressure against the diaphragm will maintain the pressure and stop any seepage.
in most data books for this system it is shown that the critical time for maintaining these pressures is between 5 and 20 minutes. After a fang when the engine is switched off the under bonnet temperature increases, causing the fuel in the lines to heat up....this will usually make fuel evaporate.....but maintaining the pressure fixes this problem and will let it start when its been standing with a hot engine.



FUEL FILTER
(next to the main pump on a mk2)

Very good idea to change this at least every 2 years or so...
as the system is so reliant on pressure and clenlyness, you filter has to be in good condition.
not much to say about this filter....
it looks allot different to normal filters and has screw in fittings in both ends to cope with all the pressure.




For some strange reason K-Jet is something im very interested in! dont ask why, its just great idea...
Ive spent many dollars on books and referances to find out as much as i can, mostly on the mk2 set up and some saab and volvo stuff too.

[Golf Loon]

Thats a good explanation Benny and I too am a disciple of or a slave to Kjet.

The 3 kjet cars I have driven this week all pulse the pump when you turn the key on but not the engine. It runs for a sec and then switches off.

This allows you to prime the metering head and make sure system pressure is to the max before you crank it over. This is especially important on the 16vs which suck more fuel.

Also holding the pedal down sucks the most air, so it starts with a heap of fuel and a bang.

[86gti]

ahh, Ive got relay disabled at the moment, running a switch and fuse on it.
been like that for a while, cause im too lazy to put the new relay in...lol...
Doing a bit more research, it says some do actualy prime the fuel line..
some between 1 to 3 sec. some volvos run a lot of extra stuff on the system... said the tachometric relay system on the mk2 Kjet didnt tho, KEjet does however.....unshure about the mk1 tho...But yea, the Kjet system is a great set up!

[Jmac]

Yeah but all said and done these systems have a non return valve which is common as ( Me too a slave to the K,KE and KE3 jetronic - from nappies to Kjet LOL) Dont worry i stared on them when Shell 1st brought out the Magic unleaded burnt valves galore!!!!! We had 10 hoist at our dealership and every second 1 had an Audi 90 head off , sorry about the waffle but that was K jet prime time ( pardon the pun) Ahh rusted fuel pump and accumulators broken mounts making up pipes man you this country is lucky in that respect dont miss that one bit. Back to the beginning - best way as we would all agree is fit pressure gauge and crank. Then leave it and watch the holding pressure etc.
Cheers fellas im with yas all the way by the way!

[jayjay]

hey, thanks for all your replies guys. =] umm.. when it starts, the idle is fine and it drives pretty well. so does that mean that it can still be a fuel pump issue?