Fuel injector test

After managing to at last remove all my injectors, the rubber seals were rock hard, I finally got round to testing my injectors today. To recap car had suddenly started misfiring with a small backfire at a junction. Misfire appears to be on number 4 at below 3500 rpm ? spark appears good.

The results are…

Injector 1: (replaced 2 years ago) jet looks to be about right.
Injector 2: output only seems to be at 70%, jet wanders from left to right as sensor plate is lifted.
Injector 3: half of jet missing until sensor plate fully opened.  
Injector 4: as number 2.

Didn?t have appropriate containers to test volume of output, but I would assume from the results I need 3 new injectors. When lifting the sensor plate there seemed to be a high frequency resonance coming from the injectors ? is this right or another sign of broken injectors?

I had one spare ok injector which I swapped for no 4. I then fired it up and see how it ran, however, when I turned the key there was a small backfire and the car refused to start? I pulled an injector while my girlfriend turned the car over and when I lifted the sensor plate the fuel splattered and coughed out?

Going to experiment more tomorrow, wondered if sensor plate could be sticking (although lifting makes no difference). Just thought I should slo check to make sure that I haven?t emptied the tank testing the injectors ops: (unlikely).

Has anyone got any suggestions or comments, particularly regarding refusal to start, backfire or resonating noise :dontknow:

Cheers

markwon said

 there seemed to be a high frequency resonance coming from the injectors ? is this right . Cheers

Correct - this is 'pintle chatter', opening and closing as pressure builds up and is released.

markwon said

Just thought I should slo check to make sure that I haven?t emptied the tank testing the injectors ops: (unlikely).
Cheers

…..scary when you see how much fuel comes out……!!!

Cheers Prowler - Plenty of fuel in the tank, yet car will not start? Checked injectors as per your test - injectors produce output when sensor plate lifted. Reconnected all but one line, put relay back in and turned car over as per Haynes test - no output from the injector just a dribble and splatter when I lifte the sensor plate, 'pintle chatter' can be heard.

Is this a pressure problem :dontknow: ? Injectors and fuel system seem to work when testing .

Cheers

Still no luck. Spent most of yesterday afternoon trying to get it to start - even had a go at tow starting. When trying to start whilst towing the car released a succesion of small backfires - what does this indicate :dontknow: . Anyone got any ideas as I not sure what to do next uch:

Cheers

markwon said

• injectors produce output when sensor plate lifted. Reconnected all but one line, put relay back in and turned car over as per Haynes test - no output from the injector just a dribble and splatter when I lifte the sensor plate, 'pintle chatter' can be heard.

Cheers

….engine will NOT start if you do not reconnect the air induction pipe from the metering head to the manifold, as all you are doing is putting neat fuel into the cylinders……..not the correct air/fuel mixture………..hence the 'backfires' in your next post?…… (you state you can lift the air flap….you can't get to the air flap with everything reconnected………..or am I mis-reading this??)
Everything must be reconnected……….BE VERY CAREFUL if one injector is out, that you dont spray fuel over the engine.

Cheers, Prowler - sorry I wasn't totally clear there. I tested an injector with the engine turning whilst stationary to see what the injectors were doing under normal starting conditions as it would not start. This is when the injector appears to splutter and cough fuel out and not spray it out in the manner in which it does during the test?

I then disconnnected the cover over the sensor plate to see if by lifting it I could increase the output of the injectors whilst the engine was turned, but made no difference. When I took all the injectors out and conducted full test again they all produced a strong output . I then reconnected everything and tried starting and tow starting it - the backfires only occured when tow starting not stationary starting?

When stationary starting the engine does even catch, misfire or backfire so not a single combustion or explosion is occurring. Am I missing something obvious here  

Cheers

………..ooer………..
I could be wrong, but…

1. I think your fuel system is ok……….you get spray patterns when doing the test. You will never be able to check a spray pattern with one out / turning engine either with or without air induction pipe connected. I can't quite get my head around this at the mo .

I am NOT trying to cause alarm and despondency (?)…..

2. Something - (past memories of my Passat when it threw it's toys out of it's pram - valves actually) - is saying "check your cam belt". It developed a strange misfire, a small backfire……then stopped. Try to restart and it backfired a few times. We worked out that the cam belt was so worn it had slipped a cog first, then just gave up by stripping itself !!!!…………I hope this is NOT the case!

Prowler - cambelt is fine . Decided to go back to basics this afternoon to ensure everything is covered. Checked ignition system - all fine. So went back to fuel.

Decided needed to see what injectors were doing when engine was trying to start. Had carried out Prowler?s test and found spray patterns on three not to be perfect. Yet they were providing an output that should have made some combustion.

Pulled all injectors and positioned them in a big jug which I held away from the engine - also laid thick blanket over the battery, HTs to smother any sparks ? obviously need to be very careful 8O . My friend turned the engine whilst I watched the injectors. On turning the engine nothing came out of the injectors, yet scarily the engine leapt into life :scratch: . After initially bemusement worked out car was firing of petrol from cold start injector.

Decided next to see if I get could fuel to come out of the injectors by lifting sensor plate with engine cranking over. Lifting the plate produced fuel out of the injectors. Next put injectors back in manifold and tried starting with myself lifting and lowering the sensor plate. However car would not start. Re-reading the Haynes, and bosch manual appeared to imply that at low revs such as starting the sensor plate pulses up and down slightly as the engine sucks in air. As a long shot had a go at mimicking this action with the sensor plate whilst my friend turned engine over. As if by magic engine sprang into life and kept running as long as I gently lifted the sensor plate up and down.

After reconnecting everything the engine started first time. However it will die unless revs are kept above 2250 rpm and sounds likes it misfiring below 3500-4000 rpm. Tried starting with cold start and warm up reg power connectors disconnected car would start without warm up reg connected, but not without cold start connected.

So I am little baffled by all this. I know from the injector test that only one of my injectors is up to spec. The others are inconsistent and jet until sensor plate is fully opened, they all look ok with sensor plate fully lifted. I assume the dodgy ones could be causing misfiring at low revs? My sensor plate could be unbalanced and wanting to shut down the fuel supply unless a lot of air is being sucked into the engine. Have checked the gap around it with a feeler gauge and gap is ok. My cold start injector appears to be working as it is squirting fuel into the manifold, enough to start the engine. I would have thought disconnecting the power to the warm up reg on a cold engine would make a noticeable difference when starting, but it doesn?t? Does this mean my warm-up reg is dodgy? Going to get a multi meter out tomorrow and test it

Sorry for the very long post ops: .

Any comments welcome

Cheers

markwon,

I know you don't want to hear this but you will not be able to diagnose the fuel system unless you do the full set of pressure tests.

You may well have a dickey warm up regulator which is causing a lean mix at cold start or a sticking fuel distributor plunger.

Cheers crazyquiff - thought as much, all the manuals I have read seem to refer to checking system pressures when carrying out diagnostics. Do you know anywhere in the UK that does them? Almost bought one from online US car parts company (?40) couple of weeks ago - would have had it by now . Is it still worth checking components with a multimeter - won't show any fuel pressure problems, but would show any electrical faults in the componants.

If that was the one from JC Whitney I'd say order it now and you may get it in a week or so if they have stock.

I got one for myself and Rich (crazyquiff) and they look OK quality wise - a lot cheaper than anything available in the UK at any rate and as Rich says essential for any kind of fuel problem diagnosis.

Cheers,

Chris

Just convert it to twin carbs and chuck the injection system in the bin.

Seriously though, it could be a problem with the 5th injector.  Think about it.  With no injectors fitted in the car, there is enough fuel for it to start and run - you add injectors and what you are effeciely doing is adding fuel, perhaps its getting too much fuel.

The funky little flap thingy should be pulsing up and down as this controls the injector pulses.  I know K-Jet is supposed to be a Continuous Injectorion System (CIS) but everything I have read about it tends to refer to injection pulses.  With the flap all the way open its probably getting way too much fuel.

I don't know if any of this is helping at all or if you know it ll lready but it might be worth having a look at http://peugeot.mainspot.net/tips/k-jets.shtml which has a full description of the systems operating including tips for setting fuel pressure (and therefore mixture!)

Another site worth of a skim over is http://www.ford-capri.fsnet.co.uk/whiterose/Injection.htm as it includes diagrams of all components with indication of what wiring goes where (ie. some reference point for our multimeter)

Best of luck!

If all else fails you may find it cheaper and easier in the long run to drop the car into a Bosch fuel system agent - otherwie you will be on for weeks on end and end up replacing everything only to find a blocked fuel filter (or something equally silly).

Kind Regards,


Steve Matthews
1983 Driver on roaring forties…

PS. You can hit me for this if you like but…

…you have checked the condition of the fuel filler neck and fuel lines havn't you?

PPS. Have you tried soaking the injectors in carburettor cleaner and seeing if that improves the flow rates/pray patterns?

Cheers Steve

Just convert it to twin carbs and chuck the injection system in the bin.

Very tempting, what sort of power increase would that give on a 1600 GTI? Sure would sound good :twisted: .

Been playing a bit more with the car and got it running by richening the mixture a turn or two. Car is is still missing at low revs if I hold the throttle at 2500rpm+ it will smoooth and fire correctly at points.

Checked injectors again last night and swapped them over. This confirmed that the bad spray patterns are the injectors and not the system. They all look good on full load, but sevaral are jetting and dribbling on partial load - the good one produces a fine atomised mist on partial load.

Filler neck is solid - was done by previous owner 5 or so years ago. Had taken most of fuel injection sytem apart, checked and soaked it in petrol and injector cleaner due it failing to fire on all cylinders at low revs - ignition system is all fine. All turned into a nightmare really as several of the injectors haven't been out for years and seals were rock hard and ended up having to build my own extractor from a fence bracket to pull them out.

I would assume form my latest test that I need new injectors even if they aren't the sole cause of my problems :roll: .

If you have access to an air line then blast any muck through them after soaking them in carb cleaner or petrol over night.

On both my cars my injectors were leaking after turning the engine off causing the engine to flood ready for the next time the car needed to be used.

Worth a try before spending ?100+ on new injectors like I did for my cab. Giving them this treatment to my '83 GTI sorted them out nicely.

Cheers,

Ross

Well - I decided to get one new injector so that I had something as good refernce point. Cost ?31 from Bosch service centre - ?34 at GSF. Couple of my injectors do appear less than perfect, but didn't cure the misfire :? . Quickly worked out what it was though…. THE HT LEAD doh doh doh      ops: .

Had checked HT leads off plugs and with plugs out, but got so bogged down forgot to swap them and check them fitted to see if they were failing under load 8O … Engine running nicely now - we live and learn. Think I will replace the other two injectors if blowing through does not improve them though as looked poor on partial loads.

Cheers

Glad you found it  

I had a similar experience when trying to diagnose my fuelling problem. Although the warm up reg was knackered, it also turned out I had a duff coil too  :roll: .

My advice would be if you have running problems and you are still on the original coil or the HT leads are looking a bit tired then replace them anyway. It doesn't cost a fortune and its extra piece of mind come winter time. I think I remember reading somewhere that the most common cause of breakdown is usually failure of an electrical component (coil / ht leads / alternator / dizzy)?

Cheers,

Chris

New leads for me then! Hope it cures my problem too!

Cheers Chris and Crazy - great to be driving a gti again. Only been of the road a couple of weeks while I sorted this and a few other issues, but thats cold turkley to me :twisted: .

Yet again the culprit is Beru HTs from GSF. Anyone else had problems with these. In my experince they complete and utter rubbish. This set had only been on my GTI a year and a half. Also had a set complety fail on the C overnight, working fine one day, no inbdication of an issue then next morninig car would not start, could not even jump start. New of HTs cured it instantly.

Cheers

Al - I'd suggest getting the pukka Bosch ones from VW main stealer. Going to get some myself today.

Cheers