Felicia Fuel Pump / ECU question

[cjiom]

Hi All,

My first post so I hope I don't upset anyone!

I'm been bashing my head on a problem with a 1.3 Felica MPI not starting (sometimes).

When it won't start it doesn't seem to turn the fuel pump on.

Leaving it several minutes usually cures the problem and it will start.

Turning the ignition on the fuel pump seems to prime for about 10 seconds and turn off.

It will do this 2 or 3 times usually and then doesn't come on any more until left for several minutes.

From the wiring diagrams (Haynes) it appears that the ECU grounds the fuel pump relay, causing it to close and power the pump (and injectors etc). When the pump doesn't run it appears that this (if I remember right the blue wire on AA) stays ungrounded.

I've done what I think is obvious which was to change the relay. I've also checked and cleaned the connections on the ECU and the Imobiliser box behind the clocks.

I can't find any description of what / why the fuel pump is controlled like it is, does it just run for 10 seconds and then the ECU turns it off until the engine turns over or is a sensor involved?

Has anyone seen something like this before of have any thoughts on this?

Many thanks in advance, if I've missed a posting covering this (I have searched honest guv!) please point me in the direction :-)

Cheers,

Chris

[TeflonTom]

the fuel pump, does prime for 10 seconds or so on it's own when the ignition is turned on. and yes you are right in saying the ecu controls the pump thereafter.. it's done like that so the pump only runs when the engine is going.. iirc the fuel pump relay also powers the ignition transformer and evap purge valve.

although it is possible that the ecu is at fault, it is unlikely. it might just be a corroded connection at the ecu..

[cjiom]

the fuel pump, does prime for 10 seconds or so on it's own when the ignition is turned on. and yes you are right in saying the ecu controls the pump thereafter.. it's done like that so the pump only runs when the engine is going.. iirc the fuel pump relay also powers the ignition transformer and evap purge valve.

although it is possible that the ecu is at fault, it is unlikely. it might just be a corroded connection at the ecu..

Thanks! Glad I'm not too far off the mark... I've had a look at those connectors and they looked ok to me (have been given a squirt of contact cleaner too since then). Nothing nasty and white or similar in there.

What I don't get is it usually cycles a couple of times ie first and second power on, but not subsequent which I think it always used to. The relay doesn't click there after so it's not the pump that's not doing it's thing as it is unpowered. Turning the ignition off for a couple of minutes seems to reset whatever it is, but that doesn't mean much to me, I was wondering if there was a sensor that told the ECU the fuel line was pressurised but the pressure relief valve appears to be purely mechanical,

I'm going to see the local garage that was the Skoda dealer tomorrow in the hope that perhaps they still have someone from their Skoda days there (they lost their dealership when Skoda decided everyone had to have the big shiny new showrooms in the early 00s). Otherwise I guess maybe the VW dealers will have seen something similar with the Caddy (I'm on the Isle of Man so the nearest Skoda dealer is now an 8 hour and £170+ ferry ticket away)

I've also got a VAG-COM cable on the way in the hope that there may be a tell-tale error in there somewhere. I actually like my Felicia, nobody else does but I think it is much better to drive than many other similar small cars I have tried.

Anyway thanks for the info, much appreciated.

[TeflonTom]

there is no pressure sensor in the fuel lines telling the ecu stuff.. the pump runs at a constant speed, which pressurizes the fuel line, then the regulator on the end of the fuel rail keeps the pressure constant and feeds the excess back to the tank.. there's no fancy sensors involved.. the pessure regulator is pneumatic(vacuum) operated

in the morning i'll dig out the wiring diagrams and apply some logic to the problem when i'm not merry on carlsberg

Edited 15 November, 2010 by TeflonTom

[cjiom]

Great, thanks.

Have picked up a Maxscan VAG405, that has got rid of the Airbag light.

Has given me 2 codes from the engine.

17978 -163

KWP1281

and

00522 -158

KWP1281

From what I can see the 522 code means the temperature sensor is likely to be dead. I've read they do fail so will get on to that and replace it, easy enough job.

The other is (I think) an imobiliser error, would I be right in thinking that this error means that at some point the imobiliser has been activated and prevented a start or does it mean that it is currently activated?

RE the wiring diagrams, is an original one available anywhere? I did buy a manual CD from ebay but it appears to only cover the felicia 1.6 not the 1.3, unless I'm being blind

Thanks for the comments on the fuel pump, a little more insight is good. As for the carlsberg, would probably fix the problem for me too, at least stop me noticing it if I'd had to much to drive :-)

Cheers!

[RobinSLXi]

Does it not start at all, or start then die almost straight away? If it's the latter, then it could well be an immobiliser issue - as you rightly guess, the 17978 code "Engine start blocked by immobiliser" just indicates that this has happened at some point. It seems quite common for the immobiliser to fail to read the key properly if the battery voltage is low. There's certainly no harm in clearing the fault code and seeing if it comes back.

My diagrams say the fuel pump relay coil gets 12v from the ignition switch via AA/10, and AA/9 goes to the ECU, which presumably chooses whether or not to switch it to ground, thus closing the relay and sending 12V through AA/8 to the pump circuit. I can't say for sure, but I suspect the ECU would shut off that circuit as part of the process if it doesn't get the OK from the immo box. Tom was pretty much right - on the 1.3MPi the circuit powers the fuel pump, injectors, lambda sensor and the evap valve (SPi and 1.6 are marginally different, but pump, injectors and lambda are common to all).

[cjiom]

Does it not start at all, or start then die almost straight away? If it's the latter, then it could well be an immobiliser issue - as you rightly guess, the 17978 code "Engine start blocked by immobiliser" just indicates that this has happened at some point. It seems quite common for the immobiliser to fail to read the key properly if the battery voltage is low. There's certainly no harm in clearing the fault code and seeing if it comes back.

My diagrams say the fuel pump relay coil gets 12v from the ignition switch via AA/10, and AA/9 goes to the ECU, which presumably chooses whether or not to switch it to ground, thus closing the relay and sending 12V through AA/8 to the pump circuit. I can't say for sure, but I suspect the ECU would shut off that circuit as part of the process if it doesn't get the OK from the immo box. Tom was pretty much right - on the 1.3MPi the circuit powers the fuel pump, injectors, lambda sensor and the evap valve (SPi and 1.6 are marginally different, but pump, injectors and lambda are common to all).

Yeah that matches my reading of the haynes diagram and sitting down there with a meter between it and the chassis.

It runs fine most of the time which is just odd I read that imobiliser error out after driving home from work with the engine still running.

What I was seeing when testing was that turning the ignition on and letting it prime for a few seconds it would turn the pump off, cycling the ignition again it does the same thing, but after 2 or 3 cycles the fuel pump (and relay) no longer come on.

Though testing the other day with it hot the engine would start even though the fuel pump would not come on when it was switched on.

I guess next time it refuses to start I need to pull out the code reader and see if that Immobiliser code comes back, perhaps cleaning the contacts on the pickup coil and the immobiliser coil have done the trick. It's more annoying as undiagnosed electrical faults usually come back to haunt me at the wrong moments (like half way round a roundabout in rush hour lol)

Thanks for digging that info out. I'm guessing there is not a lot of info on the immobiliser circuits in the documents. Hopefully it'll be something simple when it comes to it

Cheers!

[davisond619]

Hi where is the fuel pump relay and what does it look like. Car will not start and has blown fuel pump fuses several times but not blowing anymore but no fuel being pumped. Located the pump under the seat and only 4v getting there. Ant help out there?

[djaychela]

It's in the fuse box with all the others - not sure which one though, alas. Someone will be able to help, I'm sure. Try pulling them to find it?