Help! GTi motor in sierra blowing fuel pump fuse

Post by **GRPABT1** » Sat Mar 28, 2009 2:56 pm

My sierra cut out about 100m from my house today, it seemed to miss a few times before that but now won't start. The problem is the fuel pump is not starting and it keeps blowing a fuse which I assume is the fuel pump fuse. When I bridge this with a wire the car will not even turn over at all. I think it only runs the one external pump and it's a commodore pump (could there be an internal lift pump also? it's a sierra tank). I have another pump I can swap in from my V8 commodore but I am concerned about why it is blowing fuses and also won't turn over with it bridged. Any ideas before I call an auto electrician?

Post by **nicbeer** » Sat Mar 28, 2009 3:01 pm

Try run the pump with some separate wires only to eliminate it.

mine runs two pumps but afaik u cant fit a internal to a sierra tank very easy. only one wire coming from the tank? (gauge wire)

sounds like pump has gone short circuit.

Post by **GRPABT1** » Sat Mar 28, 2009 3:05 pm

Yeah I can only see the gauge wire connecting to the pump. I've traced the fuel pump wire all the way back to the main loom and can't see any damage. I'll go try a different wire now and if that doesn't work I'll pump the v8 pump in

Post by **GRPABT1** » Sat Mar 28, 2009 3:32 pm

Well the pump works when I just run a wire off the battery to the positive terminal and it does pump plenty of fuel (pulled a hose off). But even with the with the fuel pump running it won't start, just turns over. When I bridge the terminal that is blowing fuses as I am cranking it over the starter motor stops completely. I am bloody stumped by this.

Post by **zookster666** » Sat Mar 28, 2009 3:39 pm

Do you have spark? i have had a similar problem with an efi engine turned out i had a broken earth wire and stopped everything.

Check for spark.
Check for a signal from computer to the fuel pump relay.
And check your ecu relay.

cheers jesse

Post by **GRPABT1** » Sat Mar 28, 2009 3:50 pm

No spark either.

Post by **GRPABT1** » Sat Mar 28, 2009 4:21 pm

I just tried running a wire from the negative on the battery to the engine block and running the fuel pump off a wire and it still won't start. So I assume the ecu relay or ecu itself is stuffed. Does that sound right?

Post by **GRPABT1** » Sat Mar 28, 2009 4:27 pm

I can find only 3 relays, one is a black 40 amp 5 pin that seems to be not factory installed and has wires with crimp fittings attatched to it and it's on the drivers side of the engine bay on top of the inner gaurd. The other two are on the passenger side coming off the main loom not far from the ecu which is under the glove box, there is a green one and a brown one, both 5 pin and they appear to be factory installed with proper connections.

Problem is these two are a mistery as they have stickers for labels which are illegable, they are japanese made though so I assume they're factory from the original swift. Any idea what these two relays are or what amperage so I can get replacements?

Post by **nicbeer** » Sat Mar 28, 2009 4:31 pm

relay is cheap so worth a try out. (does it click)

make sure all fuses inc fusable linc's are all good.

also i guess nothing else is dead? only spark and fuel no good.

i'd maybe follow the wire off the ecu/relay if it works and you may fine a broken earth or fuse/positive.

Post by **GRPABT1** » Sat Mar 28, 2009 4:37 pm

But which one is the ecu relay? everything is fine cept for fuel and spark afaik, accesories, lights, thermo fan, starter motor. That one 15amp fuse is the only blown one.

Post by **nicbeer** » Sat Mar 28, 2009 5:04 pm

hmm. mine are next to each other in the loom.

Not sure where ur would be.

stock ecu? wheres it mounted.

Post by **GRPABT1** » Sat Mar 28, 2009 5:13 pm

Well the two stock looking ones are right next to each other on the loom. a green one and a brown one. I'll replace them with some 30 or 40 amp ones when I can get to supercheapy. It's a stock MK1 GTi ecu and it's mounted under the glove box. I'll have to get lifts to work this rotation though, awesome

Post by **nicbeer** » Sat Mar 28, 2009 5:21 pm

Try swap them round.

also i think the computer will stop the cranking of the fuel if there is no spark.

not 100% sure on this but.

Post by **GRPABT1** » Sat Mar 28, 2009 5:28 pm

Just tried to swap them but realised the brown one is actually a 6 pin lol and the green is 5. All my commodore's relays are 4 pin so no luck there either. I'll get some new relays on wednesday when I am on night shift.

Post by **Rotazuk** » Sat Mar 28, 2009 5:52 pm

The one with pink wires is the fuel pump relay and the one with white/blue or white/green wires is the main ecu relay . Well thats the way it has been for all the suzuki looms I have stripped down .

Chris

Post by **flickaz** » Sat Mar 28, 2009 7:31 pm

Im having a little trouble following this thread but I just thought Id add that not all relays are the same. You will find the pin designations of an aftermarket relay ie narva are different to a stock commodore (bosch) one, for example. Im not sure if you know how to check but if you look on the relay itself it will have a diagram showing the switch side and the coil side, this will correspond to numbers under the relay adjacent to the pins, make sure the replacement relays match or you'll end up wit all sorts of issues.

My only other suggestion is generally ecu's control auxillary components and relays by switching earths. If you've got multiple issues, ie no cranking/spark/pumps/thermo's etc I'd look for the main earth to you're ecu, or any relays/junctions that are common to all the affected systems. Ill bet when you find it you'll kick yourself, can be very frustrating, trust me I know, I do it on aircraft for a living

Post by **GRPABT1** » Sat Mar 28, 2009 8:11 pm

The problem is with the two relays I have there is no diagram and the only writing is the brand name and made in japan. My commodore bosch ones have plenty of info as does the after market one which is probably for the thermo fan.

Post by **zookster666** » Sat Mar 28, 2009 9:59 pm

have you checked the fuses for the relays all the ones i had in my gti powered zook were after market.
Also the ecu switches earths rather than power, like i said on my old patrol an earth wire broke free from a crimp and when going around a left hand bend it would break free and kill everything fuel pump, spark, and a couple of other things but would still crank over

so its either a relay
fuse
broken earth
or even possibly the ecu itself

hope this helps

cheers jesse

edit it could also be the ignition source make sure when you work out which relay is the right one that it clicks and has power to pin 86 when you turn the ignition on

Post by **flickaz** » Sun Mar 29, 2009 12:51 am

You can work out what pin is what with a multimeter and 5 minutes of time. Basically you should get continuity between 2 of the pins, these are the switching pins and are what energises the internal coil to pull the contacts together. one should have either a constant power and the other a switched earth (by the ecu) or vice versa, I'd suggest probably the first. Then if its a 4 pin relay the other 2 should be either open/close circuit until the relay is powered. you can check this by putting the previous pair of pins on a battery (you'll hear the relay click) and you should now have the opposite continuity between the second set of pins. If you have a 5 pin relay then it may get confusing for you. You will find that you will have 2 pairs of pins that have continuity without the relay powered but only one pair will make the relay click, this is because the other pair is whats called a normally closed set. The purpose of this is so the relay can power one thing when off and another when on, and use a common power line.

Im guessing either you have a basic understanding of relays and auto electrics, in which case Im making you suck eggs here or I've just confused the hell outta you. If you need me to clarify anything just let me know, maybe I could find a descent diagram to explain if I need too.

Hope Ive helped.

Post by **GRPABT1** » Sun Mar 29, 2009 5:03 am

Yeah for the record I hate electrics lol. I've got a mechanic mate who is a bit of a GTi whizz kid so I'll get him to have a look at it I think.

Post by **GRPABT1** » Mon Mar 30, 2009 7:24 pm

Well with more ass than class I just got it going. My dizzy is spewing out oil internally (common GTi problem apparently) so I was degreasing it to get it ready for a mechanic to look at tomorrow and in the I also fiddled with some wires around the coil (there is quite a few of them) and then gave it a hit of contact cleaner. After that I bridged the fuse again and all of a sudden the fuel pump kicks in when I turn the key to on and then it turned over first go! So I put a 10amp fuse in for now as that is all I have and I'll give it a proper test run tomorrow when I go get some more fuses. At least I now know WHERE the problem is. I think that fuse is for ignition coil and I assume the ECU knocks out fuel when the ignition is out like someone suggested.

Post by **zookster666** » Mon Mar 30, 2009 7:46 pm

good to here you got it goin mate

cheers jesse

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Help! GTi motor in sierra blowing fuel pump fuse

Help! GTi motor in sierra blowing fuel pump fuse

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