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 Post subject: No injector pulse randomly at start up
PostPosted: Sun May 12, 2019 4:32 am 
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Someone might be able to help me.. Swift gti

I replaced tps, maf, water temp sensor for ECU, ECU, injectors tested, fuel pump, distributor and complete assembly of the coil pack, changed grounds and basically everything that came to my mind that could cause this

The problem is no injector pulse, but it doesnt happen all the times, but when it does, is only on start up, after the car starts, there is the pulse everytime and the car runs perfectly fine.

The problem is more common on the second start up, for ex: crank for the first time in 10min without driving, starts up in a second, turn it off right away, and if i try to start it again, there is no more pulse. I have a 12v directly to the injectors, click the button once, fuel gets injected and car starts right away with that method.

The car also starts perfectly all the times if i push it down the road and release the clutch.

Anyone ever had the same problem?


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 Post subject: Re: No injector pulse randomly at start up
PostPosted: Sun May 12, 2019 7:47 am 
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I would be looking at the CAS or the earths to the motor.

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 Post subject: Re: No injector pulse randomly at start up
PostPosted: Sun May 12, 2019 8:10 am 
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You mean Cam Angle Sensor? the one on the distributor? I changed the distributor from a perfectly running gti and it made no difference, i was thinking it could also be the wiring to the ecu or from the ecu to injectors, but the car after starting runs without a problem for as long as you want


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 Post subject: Re: No injector pulse randomly at start up
PostPosted: Sun May 12, 2019 9:26 am 
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Location: NZ
Are your wires in the engine bay hard and cracked especially around the engine? I kept nursing the loom along but when I went to the new link ECU I rewired the entire car. If you have done everything else maybe you have wiring issues


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 Post subject: Re: No injector pulse randomly at start up
PostPosted: Sun May 12, 2019 9:46 am 
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Joined: Mon Aug 25, 2003 12:00 am
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Location: Londoninium
Battery and starter motor? Is it slow to crank. Perhaps not reaching the minimum rpm for ecu to recognise it turning, and not ordering action.
GTP


Last edited by gtpswift on Sun May 12, 2019 12:46 pm, edited 1 time in total.

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 Post subject: Re: No injector pulse randomly at start up
PostPosted: Sun May 12, 2019 10:31 am 
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Joined: Fri Oct 10, 2014 4:53 am
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Thanks for answering
There isnt much more to it so it might be the loom as swift12 said, but wouldnt that make the problem happen with the car started too? Because the pulsing problems happen at cranking, after its running it runs fine

To my hears it cranks quite fast actually, i have seen low battery starts on gti and even then they seem to start ok

Weirdest problem i have seen through the years to happen to this car..


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 Post subject: Re: No injector pulse randomly at start up
PostPosted: Sun May 12, 2019 11:58 am 
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Joined: Mon Dec 19, 2016 10:40 am
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Location: NZ
I used to be a mechanic...electrics certainly not my forte but I have seen a lot of weird stuff with electrics especially dicky contacts and broken wires. Most of my wires around the engine on my 1989 gti were very brittle and they tended to break a lot...I was having issues with the WTS and replaced the plug and sender....still the same issue until I cut that wire back about 400 mm to the less brittle part and it fixed the issue. When you say no pulse you are checking wether there is power off and on to the injectors at one of the injectors?
If there is a broken wire somewhere often they are fine when cold but not when warm...but no hesitation when it is running when warm?
Any codes?


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 Post subject: Re: No injector pulse randomly at start up
PostPosted: Sun May 12, 2019 12:56 pm 
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Yeah, i have dealt with some of those wires.. specially the ones near the water sensors..

The car has a fuel pressure gauge, and after pushing fuel (ignition, before cranking) it stays almost at 4 bar, and when cranking it remains there at 4bar, i also tested with the fuel rail off and absolutely no fuel came through any injector, only then i noticed there was no pulse at the injectors at random times

The car runs like new honestly after starting, even today i did like 70miles and the car ran perfectly, is just at cranking as weird as it looks


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 Post subject: Re: No injector pulse randomly at start up
PostPosted: Thu Jun 06, 2019 8:33 am 
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Up [-o<

Ps: Don't forget, after the car is started, the pulse is there and is absolutely fine, just at startup sometimes


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 Post subject: Re: No injector pulse randomly at start up
PostPosted: Fri Jun 07, 2019 8:50 pm 
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Location: Napier
Im gonna go for a wire that is common to the injectors that while the injectors are shaking during startup, is not making contact.

Happy hunting.

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 Post subject: Re: No injector pulse randomly at start up
PostPosted: Fri Jun 07, 2019 10:28 pm 
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Location: Australia WA
Try push starting it to see if it starts first go, as starter cranking my be causing massive current draw and loose ground or wiring. Give you an idea where to start looking.

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 Post subject: Re: No injector pulse randomly at start up
PostPosted: Sat Jun 08, 2019 10:50 am 
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Posts: 127
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Hey, someone just advised me to exchange the FI relay, the one next to the fuel pump, so i might do that this weekend and then give feedback
If that's not the reason, i will be changing all the wiring

About push starting it, the car starts just fine

I give feedback later, thanks


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 Post subject: Re: No injector pulse randomly at start up
PostPosted: Sun Jun 09, 2019 1:08 pm 
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Thats extreme, changing all the wiring and a bigger job than you think. Intermittent issues are painful to troubleshoot, but I feel like you are missing something. I seriously think you have a loose connection somewhere, or as mentioned, a massive current draw that is dropping the voltage so the ECU or relay is not working.

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