Car wont start and sputters and dies on pressing accelerator while on petrol

[RA_Kazmi]

dear friends,

please help me in a problem which is driving me nuts. i have taken my 2001 santro plus to almost 3 different electricians for complete 3 days but still none of them able to find the fault.

the problem is an under. 3 days ago all of a sudden on converting from cng to petrol, my car engine died as soon as i lift the foot off accelator. it was fine when i switched back to cng. next day i went to an electrician, he saw a sensor wire adjacent to coils out of its place sonit attached it back and problem solved. but next morning car started jerking off and on on cng specially in 2nd and 3rd gear so i shifted to petrol and it ran fine for 5 kms till it also almost died when i was slowing down at a chowk, shifted gears and this time, in first gear it was stuttering, jerking and not taking speed on pressing accelerator, i shifted to 2nd gear but still pressing accelarator harc till end the car will just moving like a snail, till i converted it back to cng and it was fine.

this time first took it to the best cng mechanic in peshawar who did cng tuning, found a broken spark plug, changed it, checked spark plus cables on volt meter, found it fine, also checked advancer found it ok. after that when i went out on try this time again it was fine on cng but as i converted to petrol, it started sputtering, occasional misfire and not taking accelerator, again switched back to cng and it was fine. checked this again and again, it was happening every time on petrol so went back to cng mechanic, he told me he thinks fuel pump is the culprit, so go to an electrician.

went to electrician, he replaced the fuel pump with a new one, problem persisted, this time, not even starting on petrol. had to start from cng and convert to petrol and again engine died. he checked fuel lines, petrol was coming freely, then he opened injectors, checked them one by one, all were fine, their sensors were taking current so he saif injectors are also fine. changed air filter, still problem was occuring on petrol. it took me late till evening so finally brought back the car as it was too late.

now i am at loss. car is fine on cng. but wont start ( just keeps on cranking) on petrol. no check engine light comes on. sputters on petrol and completely shuts off on pressing accelerator if on petrol.

please some one help me. even electricians have failed to diagnose. what could cause this problem

[aamirq]

when was the last time u had the cars throttle body serviced?

[RA_Kazmi]

It was December 2013 when the injectors, along with fuel rail and throttle body was cleaned. Do you think it is a throttle body issue because it fails to start on petrol despite engine cranking and engine sputters and then dies on pressing accelerator cable when switched from cng to petrol. Please see that it doesnt give any problem on CNG. Do you still think it is T.B issue because its only a problem on petrol

[Naweed]

dear friends,

please help me in a problem which is driving me nuts. i have taken my 2001 santro plus to almost 3 different electricians for complete 3 days but still none of them able to find the fault.

the problem is an under. 3 days ago all of a sudden on converting from cng to petrol, my car engine died as soon as i lift the foot off accelator. it was fine when i switched back to cng. next day i went to an electrician, he saw a sensor wire adjacent to coils out of its place sonit attached it back and problem solved. but next morning car started jerking off and on on cng specially in 2nd and 3rd gear so i shifted to petrol and it ran fine for 5 kms till it also almost died when i was slowing down at a chowk, shifted gears and this time, in first gear it was stuttering, jerking and not taking speed on pressing accelerator, i shifted to 2nd gear but still pressing accelarator harc till end the car will just moving like a snail, till i converted it back to cng and it was fine.

this time first took it to the best cng mechanic in peshawar who did cng tuning, found a broken spark plug, changed it, checked spark plus cables on volt meter, found it fine, also checked advancer found it ok. after that when i went out on try this time again it was fine on cng but as i converted to petrol, it started sputtering, occasional misfire and not taking accelerator, again switched back to cng and it was fine. checked this again and again, it was happening every time on petrol so went back to cng mechanic, he told me he thinks fuel pump is the culprit, so go to an electrician.

went to electrician, he replaced the fuel pump with a new one, problem persisted, this time, not even starting on petrol. had to start from cng and convert to petrol and again engine died. he checked fuel lines, petrol was coming freely, then he opened injectors, checked them one by one, all were fine, their sensors were taking current so he saif injectors are also fine. changed air filter, still problem was occuring on petrol. it took me late till evening so finally brought back the car as it was too late.

now i am at loss. car is fine on cng. but wont start ( just keeps on cranking) on petrol. no check engine light comes on. sputters on petrol and completely shuts off on pressing accelerator if on petrol.

please some one help me. even electricians have failed to diagnose. what could cause this problem

i'm unable to comprehend the situation, still trying to assist in finding the fault :

-- first how can a plug break unless it is hit internally by the piston or it broke while unscrewing, meaning it was over-tight with rusted threads .. if the piston hit it, then be ready for an engine job

--- how can an electrician change a fuel pump without checking it since later when the symptoms persisted, the same electricin checks fuel pump and fuel line but by then the fual pump had already been replaced .. are u sure, previous one was not working .. why did u not ask the electrician about this ?

the items which do not function while car is running on cng

-- injectors (technically .. virtual signals are being sent to ecu)
-- fuel pump

the items which can create a difference while car runs on petrol

-- air-supply (sometimes chocked for cng causes prob on petrol)
-- idle adjustment (same as above) and related items
-- timing -- the advancer controls it, in ur situation
-- cut-off valve (which cuts off petrol when car is on cng and vice versa)
-- conversion switch for cng to petrol .. (the switch inside the passenger cabin which u press for conversion)

the situation dictates that when u convert to petrol no or very less petrol is coming. i think it is cut-off valve or the switch controlling it or some relay which assists in the conversion .. even if cng is not properly cut off the mixture of cng and petrol plays havoc

just to check which way is the fault .. turn off cng from cylinder and then convert to petrol and try starting the car .. if you dont get anything that means cut-off valve is not operating .. a cng mechanic with little knowledge, can also bypass this valve to double ensure because sometimes advancer also mis-behaves in a pattern, where petrol runing is disturbed

[aamirq]

try getting the throttle body serviced and even get the IACV serviced it should help! im sure the cars throttle body is full of carbon and totally choked up!

[RA_Kazmi]

dear naweed. thanks for such a detailed answer. one spark plug whitish portion where the spark plug cable attaches had a big crack, may be because of over tightening. the electrician initially told me that the fuel pump is weak because he was pulling accelarayor spring and the with the spring getting pulled car was stuttering more and more, while it should have accelerated. so he changed it with another one but when the problem still persisted he fitted the old back into its place.

where is the location of the valve which cuts off cng from petrol. he electrician today did one thing, and perhaps he was checking the same, he turned the cng switch to petrol and then disconnected the cng pipe end adjacent to t valve on cng pipe coming from the cng kit, and still car was not starting on petrol.

and how can one find fault with the cng switch that is fitted inside the car beneath the steering wheel. and how to kmow if its advancer. cng mechanic told me that advancer is ok. he opened it and checked it on some voltmeter sort of thing. i dont know what it was.

[RA_Kazmi]

dear aamirq
if the throttle body is chocked, wont it give problems on cng too as the air has to come from this way whether it is petrol or cng

[Naweed]

dear naweed. thanks for such a detailed answer. one spark plug whitish portion where the spark plug cable attaches had a big crack, may be because of over tightening. the electrician initially told me that the fuel pump is weak because he was pulling accelarayor spring and the with the spring getting pulled car was stuttering more and more, while it should have accelerated. so he changed it with another one but when the problem still persisted he fitted the old back into its place.

where is the location of the valve which cuts off cng from petrol. he electrician today did one thing, and perhaps he was checking the same, he turned the cng switch to petrol and then disconnected the cng pipe end adjacent to t valve on cng pipe coming from the cng kit, and still car was not starting on petrol.

and how can one find fault with the cng switch that is fitted inside the car beneath the steering wheel. and how to kmow if its advancer. cng mechanic told me that advancer is ok. he opened it and checked it on some voltmeter sort of thing. i dont know what it was.

next time use mention, quote or like option so that the person u r addressing to gets a notification and knows where to reach

for the cut-off valve or actuator and the conversion switch you'll have to go to a cng fitting expert .. i cannot make u understand all of it by just explaining theory .. the same valve that electrician checked was suposed to be checked by a cng mechanic and to be certain he has to bypass petrol line .

[RA_Kazmi]

you mean to say that before i go to another electrician, i should go the cng mechanic who had initially fitted the switch and cng dial etc, and after that i should go to the electrician

[RA_Kazmi]

next time use mention, quote or like option so that the person u r addressing to gets a notification and knows where to reach

for the cut-off valve or actuator and the conversion switch you'll have to go to a cng fitting expert .. i cannot make u understand all of it by just explaining theory .. the same valve that electrician checked was suposed to be checked by a cng mechanic and to be certain he has to bypass petrol line .

so i should go first of all to cng mechanic tomorrow morning to ask him to check switch and valve and then to some electrician.

[Naweed]

so i should go first of all to cng mechanic tomorrow morning to ask him to check switch and valve and then to some electrician.

yes, i think that one of them is not working properly .. find a shop which fits cng kits and have these items in stock .. hopefullythis will get solved .. best wishes

[Naweed]

you mean to say that before i go to another electrician, i should go the cng mechanic who had initially fitted the switch and cng dial etc, and after that i should go to the electrician

if the fault is in the cng system, u might not need help from an electrician .. plus i don't like this electrician who tried fault finding earlier :).. if at all required go to another electrician ...

[Naweed]

the shops where kits are dismantled and cleaned are also quite expert

[RA_Kazmi]

the shops where kits are dismantled and cleaned are also quite expert

Today in the morning, I took my car to a CNG Expert who installs and fixes CNG Kits and told them the problem and asked them to check CNG Switch and Cut off Valve. They disconnected Gas and then checked the wires, circuits, ran some tests, and told me that no problem in CNG switches and circuits. Go to a mechanic or Electrician

This time, I went to another Electrician who had a good reputation with EFI Cars. He first checked currents in Injectors wires, found them ok, then took the petrol inlet and outlet tubes coming from fuel tank and told me that the fuel is coming to fuel rail but not going back. The Fuel Pump motor is weak. We took out the old pump and went to an old engines market and bought a good kabuli fuel pump. He fitted it the new pump and boom, the car started with single ignition. He converted back and forth to cng, we did test drives on low speed and high speed and everything was OK. car was starting normally, no sputtering, nothing. Everything was back to smooth.

Bottom Line: The initial electrician who changed the fuel pump for the first time had only checked the fuel in line but didnt bother to check the fuel outlet line. first time when he changed the fuel pump, probably he had installed another faulty pump, which he had with him and probably had taken out from some other faulty cars (as some mechanics these do these sorts of things, taking out semi faulty components from one car, keeping it with them just to fit in another car and make some money). So the second pump was also faulty, after which he installed back the original faulty pump. So today when a good quality pump was fitted, everything was fine. The whole process took 40 minutes. Problem solved.

P.S I would specially thank Naweed, and aamirq for the valuable technical input. At least these sorts of discussions gives a peace of mind and allow novices like us to know a bit or two about the cars that we drive. Buck up guys. Your help was very valuable. Thanks again brothers

[Naweed]

@RA_Kazmi i was quite certain it was a prob with petrol flow in cng, since the fuel pump had already been checked .. even i got the name of a good cng mechanic from a friend in peshawer .. note it "some famous cng guy behind shell pump & suzuki sarwar auto on warsak road" I'm glad you got the problem solved

[RA_Kazmi]

@RA_Kazmi i was quite certain it was a prob with petrol flow in cng, since the fuel pump had already been checked .. even i got the name of a good cng mechanic from a friend in peshawer .. note it "some famous cng guy behind shell pump & suzuki sarwar auto on warsak road" I'm glad you got the problem solved

Thanks Naweed. You are referring to Abid CNG Mechanic who has his workshop behind Suzuki Motors on Warsak Road. In my initial post the best CNG mechanic in town that I referred to was the same Abid Ustad as yesterday he did the initial CNG tuning in my car, found the damaged spark plug, check the wires, advancer and initially told me that the problem mots probably lies with Fuel Pump, but the idiot electrician who fitted another faulty fuel pump actually misguided himself as well as me, giving me a tough time and wastage of time