Strange Back Fire....

[lapr 4 2 Cars]

Hello chaps and chapetts, I'd like to pick your brains if I can!

After eventually getting my engine in and running (big thanks to Craig !), a tad lumpy but running! Anyway thought I'd start it up as it hasn't run for a while, which was all good ran ok, have done this twice now I think.. Went out earlier, started on the button ran and for a min or so, spluttered, back fired and a nice little cloud of smoke poured out of the air filter... It done this twice . So, after getting the ump with it and checking around it to make sure all looked as it should, I locked it up and thought I'd do a search on it, but to no avail, loads of other bits and pieces came up but nothing specifically on that...

Any one had this or similar?

Its a 1991 1.9 gti engine.

Thanks ppls!

[omega 82]

^{has it got old fuel in it}

Edited September 19, 2013 by omega

[lapr 4 2 Cars]

No, it hasn't unfortunately, or if it did it would of been minimal as the light was on when re filled...

Its run a few times for longer periods (same fuel) and never done that before?!

Very strange...

[DamirGTI 327]

Check the timing belt first .. then the ignition leads layout on the dizzy cap/cylinders , and try to advance the dizzy a little bit .. check valve clearances also .

 

Is the engine used or rebuild ? backfired on the inlet or the exhaust ?

 

D

Edited September 19, 2013 by DamirGTI

[lapr 4 2 Cars]

Its a re-built lump with about 15k on it...

Ran fine in the other car and has run whilst in this car!

Leads etc havnt been touched, was chucking it down at the time, hoping its just a moist dizzy!

Shall be looking into it further tomorrow, with a bit luck!

Cheers

[DamirGTI 327]

Strange .. something must've go bad whilst standing then .

 

Anyway , do check if the timing belt is sound before proceeding further (who knows , maybe it's the tensioner gone "loose" or something..) , ignition timing , basic stuff - leads , dizzy cap/rotor , spark plugs , coil + ignition amp (try with known good spares if you have) .. fuel filter , fuel pump (if run for too long on extremely low fuel level , or worse without it can fry the pump ..) vacuum leaks , AFM , connectors/wiring .

Do a compression test as well .

 

I really never ever had backfiring issues on this engines . If it's healthy engine , properly adjusted (engine timed up properly i.e. timing belt , ignition timing) and all the fueling/ignition components are sound it shouldn't do this .

 

D

[lapr 4 2 Cars]

Your right, it shouldn't do this!

Am thinking it may be something simple as its run with no issues before...

s*ite British weather is to blame hopefully!!!

Investigation day tomorrow, will update if the problem is found!!

Cheers

[DamirGTI 327]

Stick an potato inside a tailpipe and blame the neighbors !

 

Moisture - cod be the issue , but i somehow doubt . If it starts fine and then worsens as the engine heats up , that kinda points out to something heat related (ignition components are notorious for going bad in the prescience of excessive heat and vibrations .. and the moisture as well) .. anyways , do not take anything for granted - inspect thoroughly starting from the basics to more complex stuff and hopefully you'll find the issue

 

Might do us an video with the engine running/backfiring if you like , so that we can "narrow" the list of possible causes .

 

D

[Bananasplitz 0 1 Cars]

Your right, it shouldn't do this!

Am thinking it may be something simple as its run with no issues before...

s*ite British weather is to blame hopefully!!!

Investigation day tomorrow, will update if the problem is found!!

Cheers

Not to hijack your post but I've just had a similar experience yesterday with my 1.9. I though tinitial it may have been the weather as well due to damp conditions. As I only use the pug on the weekends, so when i started it yesterday morning it seemed to start in its usual slow way, waited for it to warm and then out onto the road, power seemed to dip, then fine, coming up to first roundabout seemed to loose power completely then touching the accelerator it sprang to life again. I turned it round headed home but it died outside the house. I managed to start it couple of times but it just seemed to slowly die.

Kept trying it, seemed to kick over strongly on the starter and seemed to be getting compression but refused to start, got a strange backfire not loud more like a phut, heard some mechanical creak/squeaks. Gave up and pushed it on to the pavement.

Found a large thin nut and washer on the ground where I had been trying to start it.

Left it overnight and figured the nut was from the alternator thought that refitting would sort it out.

 

Today I thought that refitting the nut would sort it out as the pulley would have just been spinning so thought there may not be enough electrical power from the alternator to start.

Didn't work, refitted the nut, alternator span on starting, kicked in to life ran for about a minute then died slowly again, tried starting again but same as day before engine under starter seemed strong same weak backfire/phut.

 

It has just had the timing belt changed about 300 miles ago.

 

I'm guessing the electrics are ok as it initially started??

Tank is full. Filled to top with only a couple of miles driven.

Thought it may be a fuel issue, Tried listening for the fuel pump couldn't hear any noise. Should you be able to hear the pump with tank full.

What's the best way of checking fuel without burning the car

Any ideas

Would be useful to know how you get on in case similar issue.

[DamirGTI 327]

I'm guessing the electrics are ok as it initially started??

 

 

No , not really . As i said before , the electrics , mainly ignition components do go/start to go bad whilst the engine reaches operating temp. . It's not a rule , but it's more often .

 

From the description i'd thoroughly check secondary ignition components first - start from the plugs , leads , dizzy cap/rotor . Then primary components - coil + ignition amp and they're wiring/connectors , dizzy + dizzy signal cable for breakdown/loos of signal in the prescience of engine vibrations .

If all seems to be sound ignition wise , move on to the fueling - fuel pump relay and it's wiring/connector (oddly enough , burnt fuel pump relay diode can cause similar issues - been there twice !) , fuel pump , injectors and they're wiring/connectors , fuel filter , fuel pressure .

Still no luck - AFM and it's wiring/connector (pop off the cover and inspect the black carbon track inside the AFM - look for white areas/spots across the wiper movement area or severely grooved surface.. if there is some , it'll loose the signal on that particular spot .. often , if there is overlay wiped white area it'll be on the start of the wiper movement) , vacuum leaks (mainly hoses/mating surfaces down the AFM .. sometimes you can actually hear hissing , if there is an vacuum leak) , ECU temp. sensor .

 

To be honest , i'd try an spare known good amp. first .. along with fresh layer of heat sink paste - had various performance issues caused by the bad/going bad ignition amp. . From misfiring to hard starting/cranking loos of power or no starting at all . Also , when the ignition amp. goes bad it sometimes "takes" the coil with it as well . So , try an known good spare coil along with the amp. .

Next , the AFM (overlay wiped carbon track) .

Last (till decided on the complete "tear down"/inspection) fuel pump relay .

 

Now this reminds me , i had once virtually same issue - starts fine from cold , once up to the temp. misfiring/popping/stuttering/loos of power whilst driving which made me tearing all the bits and pieces on the engine apart afterwards in searching for the cause . Only to be found on the end , after i tried all kind of tests/swaps with known good items , that one of the 4 spark plugs was faulty !! While inspecting the plugs they're all seemed fine by the looks and whilst testing for the spark , however one was clearly bad .. was something internal invisible by the naked eye and obviously heat related .

 

So , sometimes it can be as simple as that .

 

 

Should you be able to hear the pump with tank full - not with the back seats in place and sitting up front . With the rear seats folded down and sitting near the pump while someone starts/cranks the engine - yes . Also , some fuel pump relays make buzzing/priming sound with the ignition in ON position , and others don't .

 

What's the best way of checking fuel without burning the car - have no fear of burning if there's no spark or naked flame near ! fuel mainly wont be ignited by the hot surface , however spark or naked flame will ignite it so be careful . Best way (at least i like to check for fuel this way) , check the fuel filter for possible obstructions first , then - undo the injector rail bolts and pull the whole assembly along with the injectors and fuel press. reg. off the inlet manifold - leave the injectors , injector connectors , fuel feed and return hoses attached to the rail . Move the whole assembly sideways and find 4 jars/glasses/pots and place/arrange each injector tip so that it sprays into the jar/glass/pot (also , use some old rags and place them underneath ..).

Now , you can simply crank the engine and check for the prescience of the fuel in the each jar/glass/pot afterwards or ask someone to do the cranking for you whilst you watch the injectors spraying pattern and quantity .

If you wish to test the fuel pump itself , do similar - undo the main feed pipe from the rail (might be better still to undo the hose before the fuel filter to isolate the possibility of clogged filter affecting the test result , or check it before the test) , place the end of the hose into the jar/glass/pot and activate the system by cranking the engine or manually bridging the fuel pump relay/relay connector terminals .

In both cases , injectors - there should be an nice conical spray pattern from the each injector tips , ideally all the same/similar , and filling up the jar/glass/pot with the identical amount of fuel . Fuel pump flow , should be quite a lot of fuel stream coming out of the end of the hose when activating the system (there's an counting method of how much fuel it need's to deliver at certain time as well , but from the top of my head i can't remember the figures myself was always judging that by "feel")

 

D

Edited September 22, 2013 by DamirGTI

[Bananasplitz 0 1 Cars]

Thanks for your help, didn't get a chance to wotk through it all yet.

 

Today's news, went out to try to start it, after it not starting yesterday (weather yesterday damp wet mist, now dryer warmer sun out ground now dry) started first time, ran about a minute then died, left it a minute, tried again same started this time died after about 30 seconds, again this time with foot on peddle at 2000rpm ran for minute took foot of and it died, temp not yet up could hear the pump. Tried again, limp backfire but gradually seemed to pick and come to life, this time kept foot on till engine heated up 3-4 minutes took foot off and it continued to idle as normal took it for short run no with dipping of power. Left it for three hours tried again stated first time no issues idled as it should, took it for a spin actually seemed smoother. Other than prodding the wiring round the tachymetic relay under the dash i did nothing else, my only thought is damp getting to something but what I don't know?

Because it now working I don't know where to start other than waiting to next time.

Edited September 22, 2013 by Bananasplitz

[Bananasplitz 0 1 Cars]

Iapr, has the good weather sorted yours out?

[DamirGTI 327]

Intermittent problem - the hardest one to find the cause

Not much of advice , but do all the checks listed above .. even if you don't quite find a problem from any of them , on the end you'll at least have pretty good idea of what it certainly isn't .

 

If you suspect moisture is the issue - buy an can of contact spray (there's also an spacial type of spray for fine electrics like various engine management sensors/more complex electronic components.. Permatex makes one ..) , unplug the spark leads and spray into each one as well as on the external insulator side of the leads trough all the lead length , undo the dizzy cap and spray some inside and outside on the cap as well (also , check inside the dizzy cap terminals/ports - there's often whitish oxidation deposits which builds on to the terminals from time to time - take an flat pocket screwdriver and gently scrub the deposits off each 4 terminals/ports) , spray some onto the coil tower and ignition amp. connector , undo the dizzy signal cable and spray some on the inside on the terminals (it's the 3pin yellow connector which connects into the black one secured with an clip) , undo the AFM connector and spray some on it , on the ECU temp. sensor connector , injector connectors .

 

If you manage to get the engine running without dying - try to wiggle all the wiring connectors , use an screwdriver handle and tap the ignition amp. few times .. and see what happens . Pull off the rubber boots from the wiring connectors and check for pushed off wiring terminals .. chuffed wires touching earth in the prescience of engine vibrations .. stuff like that .

 

One test might be good to try as well for moisture concern issues (checking for ignition voltage leaks) - wait till it's dark outside , find an bottle with spraying mechanism , fill it with water and spray onto the ignition components (but not too much so that you're soaking them ! .. and clean them afterwards ASAP with water dispersal spray when you're done , contact cleaner or WD-40) , start the engine let it idle with the bonnet opened and turn off the lights (try to pick an spot with min. or best no surrounding street lighting) , and watch closely around - leads , dizzy cap , coil tower .. If there's an voltage leak from any of the mentioned , you'll see the spark jumping from let's say a coil tower onto the nearest metal part , or from the spark lead onto the valve cover or some other near metal part , cross sparking in between the two or more spark leads . If it's really bad voltage leak you'll often hear "clicking" sound along with the jumping spark . All combine with kinda rough engine idling .

 

Have you perhaps noticed that the rev. counter needle bounces or drops ?

 

D

Edited September 23, 2013 by DamirGTI

[lapr 4 2 Cars]

Have not had a chance to get out and have a look at it this weekend due to a noisy baby and a lippy-now grounded 7 year old!!

Curiosity has just had the better of me, and decided to fire it up, to which it did. Fine. NO backfire or puff of smoke-Been dry for the best part of a week so its definitely a moisture issue somewhere I'm guessing...

Cant trace too much if its running ok however there does seem to be an air leak somewhere (sounds like its behind where the oil filler is... Cant be to sure yet though!), wondering if that's the little s*it thats causing me agro!

Something else to look into...

Shall trace and repair that, if it hasn't rained by then to check it, I'll take me sprinkler to it and see what happens!!!

[DamirGTI 327]

 

Cant trace too much if its running ok however there does seem to be an air leak somewhere (sounds like its behind where the oil filler is... Cant be to sure yet though!), wondering if that's the little s*it thats causing me agro!

Something else to look into...

Shall trace and repair that, if it hasn't rained by then to check it, I'll take me sprinkler to it and see what happens!!!

 

The missing bolt which holds/attaches the oil filler onto the inlet manifold ? if so - definitely . It'll create vacuum/air leak straight inside the inlet manifold cos the inlet is drilled across the length on the insides beyond the bolt threads , so actually an open hole in the inlet manifold . As this hole is downstream the AFM it'll be false/unmetered air creating lean mixture .

 

Common problem of vacuum/air leak on this engines anyway , fix it by fitting the bolt back (smear some RTV on the threads before running the screw in , but just an small blob of RTV so that the bolt threads are "sticky") and see if it sorts the issue . Even if not it'll run/idle better, that hole must be plugged/closed.

 

D

Edited September 23, 2013 by DamirGTI

[Bananasplitz 0 1 Cars]

I've just had the same problem this weekend, starts initially then dies, though the third attempt I kept the revs up at about 2500 for about three mins until engine was warm with fan running, if I lifted of the engine would start to die. Almost as if being choked. This stirred me into ordering plugs, ht leads, distributor cap and rotor arm ( though wont get them till monday), then this morning i had a S.A.D thought could it be the supplementary air device remembering reading damir,s guide on what it is etc i read it again.

I now have a number of questions,

1. Could the S.A.D not working fully cause this starting problem and the lack of additional air the be the root cause of my problem or something else connected to the S.A.D be the root cause?

2. If the S.A.D fails, would it normally be in the closed position?

3. Where does the small heater in the S.A.D get its power from,

4. What other parts on the ignition circuit is the S.A.D connected to. (This may point to a common source if the S.A.D bimetallic strip is not being heated electrically, but does eventually work due to engine heat (part failure of the S.A.D).

 

I also noted what when starting and only when looking across the top of the engine slight smoking/or steam rising, not sure if this could be damp water vapour, or a water hose leak, or oil from a small leak burning off(something else to sort out). Does any one know a good place to get single oil/water pipes as I seem to only find them as sets?

[DamirGTI 327]

Wise choice - renewing main tune up parts like plugs/leads dizzy cap doesn't cost much , and it'll for sure be better for the engine even if it doesn't fix the problem , you'll rule that out as being good condition/new parts .

 

1. SAD , maybe .. doubted but who knows , the easiest way to check if it's working properly is - start up the engine from cold , let it idle for a few seconds , then go up front and pinch the SAD hose with your fingers (the SAD hose is smaller diameter one , the one opposite of the oil breather hose on the main air pipe which connects throttle body and the AFM) .

With the engine warming up , as you pinch this hose it'll have to gradually loose the revs and start to bog down . That's if the SAD works as it should . If it doesn't have any affect on the engine running/idle quality , then there's clearly something wrong with the SAD or it's pipework (more often it'll be pipework ..) . The SAD is pretty crude device , and from my experiences doesn't go wrong so often as a unit .

 

Here's an article about the SAD : http://www.205gtidrivers.com/articles.html/_/articles-guides/engine-related/supplementary-air-device-sad-r33

 

2. I believe it'll be the other way around (so opened) , but can be stuck closed as well . Can check this by undoing the SAD pipe from the main air pipe blowing trough - on a cold engine , the air must pass all the way trough the pipework and SAD to the inlet manifold without obstructions , on fully heated engine you should feel the resistance as you blow down the pipe .

Also , you can check this by undoing the pipe from the SAD and by looking inside it - "half moon" position of the bimetallic disc when cold , fully closed position without being able to see trough the SAD on the other side while hot .

 

3. The heater supply gets power from the fuel injector wiring . Also , there's more components which are connected to the same wiring as an voltage supply - TP sensor , AFM and tachymetric relay (fuel pump relay .. this powers up the circuit) . The earth side goes on the battery neg. terminal , but also cross connected with the AFM , ECU coolant temp earths , tachymetric relay and ECU .

 

4. None of the ignition components aren't connected to the SAD , while cold the bimetallic disc must be partly opened ("half moon" shape) , with the engine started and heating up it uses both the coolant temperature (it's bolted near the coolant flow block for this purpose) and voltage supplied via connector/heater to fully close up the bimetallic disc . And it really needs both , the coolant temp. and voltage to fully close up once the engine is up to the operating temp . If there's no voltage present at the connector for the heater it will close the disc (just by being near the coolant flow and thus as the coolant heats up it'll make the disc closing) but not completely ! As soon as the coolant temp. drops down a bit , when you're driving on a open road/motorway in high gear with low engine load , the bimetallic disc will start to "semi open" up again which will affect idle speed by increasing it up to the 1000/1500 revs .

 

As for the water/oil pipework , if you can't find single ones - take an sample of needed hose and ask around the car part stores if they have something similar based on a sample (usually they do .. from some other car brand same/similar pipe shape bends which just needs length timing to suit ..) . If not , can still buy them from the dealer per piece , though kinda pricey ! so i'd try the local car part stores first .

 

D