Saxo (1999) Suddenly Won't Start - Advice Pls

22nd August 2021, 14:50

Hello Everyone,

Our 1999 Phase 1 Saxo suddenly won't start - two weeks ago it was fine, now it cranks but engine won't fire. I think the fuel delivery system is the problem*, but I've no idea if it's the Pump, Relay or Inertia Switch at fault (that's all it could be I think, no?). I checked fuses and I tried resetting Inertia Switch (held for 10-15secs with keys turned to II) and neither helped.

After researching I believe it is possible to connect the pump directly to the battery as a test, so I can see if it's working. But I'm not sure how to wire that up.

The pump has four wires going into it - a blue and yellow wire (in slots 2 & 4 respectively) which are thicker, and a thinner red and green wire (in slots 1 & 5) - picture linked below. Could someone please tell me which of these four (red/blue/yellow/green) I need to run to the positive battery terminal and which to the negative terminal? Just to see if the pump runs.

The second question I'd like to ask is where on earth is the fuel pump relay. Another reply on this forum said it was under the ECU - but the things under there (see pics below) don't look like the pictures of the relay I found online. Somewhere else said behind the fuse box but it there's nothing there I can see.

Any help/advice would be hugely appreciated, the car is currently parked on the side of the road a couple of miles from the house and it would cost us a lot to get it towed. Although I'm not a super-experienced mechanic I did quite a lot of successful repairs on my last car, and I think I could fix this IF I can diagnose the exact problem - and it would save us a lot at a difficult time.

Thank you very much for your time and any advice.

*The reason I think it's the fuel delivery system is
1) The pump isn't making any noise I can hear.
2) I checked the plugs are they are definitely sparking.
3) It's hard to explain this but it's VERY hot here where we live atm (35 or more degrees) and I've been to look at the car 3 afternoons in a row now. Each time, when I first turn the ignition key the engine DOES start firing for a second before stalling, this happens once or twice then it stops firing completely. I think what's happening is it's so hot that sitting all day in the sun is causing fuel to evaporate and build up just a little pressure in the fuel lines, this is burning off when I first turn the key causing the engine to fire a few times... then nothing. So that causes me to think the engine can start but fuel isn't getting through.

Links to pictures :
The wires on fuel pump -
https://imgur.com/3csDwD3
Engine -
https://imgur.com/ChziXoj

23rd August 2021, 09:28

When you turn the ignition on, does the fuel pump prime? You have said it makes no noise at all, so just to confirm.

The wires on the pump you need are the two thicker ones (in the centre).

I didn't know there was a fuel pump relay. Only a fuse. the thing under the ECU is the fuel injection relay.

23rd August 2021, 15:11

Tyvm for replying.

I don't think it primes, although I'm not sure what signs I should be looking for. It doesn't appear to react at all when the ignition is flipped... it's completely silent.

Maybe there isn't a relay on this car... it would explain why I didn't find one! It's is my flatmates car (although we both use it) but I'm just not that familiar with it.

Hopefully I can wire up the pump directly to the battery to test. I don't know if it's possible to slip the wires out of the connector - if not I'll try to connect directly to the pins. I couldn't figure out what the red and green wires were for - I found this diagram (https://imgur.com/IJZ3YeU) but simply can't see those wires mentioned here. From another thread I read I think they might just be for a sensor of some kind or dash light - in which case not essential to make the car run.

Could a faulty injection relay completely prevent fuel getting to all four cylinders? But I think the relay is clicking when the engine is turned.

If it's not the injection relay then I guess it must either be the Pump or the Inertia Switch... the weird thing is that it went from apparently working fine with no issues, to not starting at all - I would have thought the pump would show some signs of dying before giving up.

I'm trying to borrow a multimeter from someone which would make all this easier to test - mine is broken.

Is there anything else I'm not thinking of which could completely prevent fuel from reaching the engine? I think it has to be the pump or the switch otherwise...

Thanks so much again for replying... my flatmate is so unhappy at the moment 'cos of this and work, and I really want to try and get it sorted for her if I can.

23rd August 2021, 21:54

the relay under the ECU controls EVERYTHING.

Fuel pump,injectors, feed to the coil pack.

If the relay is giving power to the coil pack, it's also giving the fuel pump power.

If the fuel pump isn't turning, either the earth is faulty, a wire is broken on the pump has simply died.

Just to confirm it is a fuel problem, pour some petrol/gas down the intake. A good 100ml or so and start the car. If it runs "normally" then 100% the fault is with fuel delivery.

24th August 2021, 10:02

Quote:

Originally Posted by MartinObviously

the relay under the ECU controls EVERYTHING.

If the fuel pump isn't turning, either the earth is faulty, a wire is broken on the pump has simply died.

Just to confirm it is a fuel problem, pour some petrol/gas down the intake. A good 100ml or so and start the car. If it runs "normally" then 100% the fault is with fuel delivery.

TYVM for the reply and info. However, I'm sorry if I'm being dense but when you say

Quote:

pour some petrol/gas down the intake

do you mean to disconnect the engine side fuel hose from the pump and pour gas directly into there? Or can I access the fuel line at the other end nearer the engine somewhere, just before the injectors?

I think our model has a connector like this engine-side, did you mean access this?

https://www.garage-mahieu.com/en/art...e-1997-x215114

Like I said, although I've done quite a lot of my own repairs over the years, I'm not a super-experienced mechanic, and I don't have a Haynes for this car which is making everything doubly difficult.

I really appreciate the advice... like I said, I'm sry to be dense.

24th August 2021, 10:04

Quote:

Originally Posted by MartinObviously

the relay under the ECU controls EVERYTHING.

If the fuel pump isn't turning, either the earth is faulty, a wire is broken on the pump has simply died.

Just to confirm it is a fuel problem, pour some petrol/gas down the intake. A good 100ml or so and start the car. If it runs "normally" then 100% the fault is with fuel delivery.

TYVM for the reply and info. However, I'm sorry if I'm being dense but when you say

Quote:

pour some petrol/gas down the intake

do you mean to disconnect the engine side fuel hose from the pump and pour gas directly into there? Or can I access the fuel line at the other end nearer the engine somewhere, just before the injectors?

I think our model has a connector like this engine-side, did you mean access this?

https://imgur.com/a/w98HxAS

Like I said, although I've done quite a lot of my own repairs over the years, I'm not a super-experienced mechanic, and I don't have a Haynes for this car which is making everything doubly difficult.

I really appreciate the advice... like I said, I'm sry to be dense.

24th August 2021, 10:06

Quote:

the relay under the ECU controls EVERYTHING.

If the fuel pump isn't turning, either the earth is faulty, a wire is broken on the pump has simply died.

Just to confirm it is a fuel problem, pour some petrol/gas down the intake. A good 100ml or so and start the car. If it runs "normally" then 100% the fault is with fuel delivery.

TYVM for the reply and info. However, I'm sorry if I'm being dense but when you say

Quote:

pour some petrol/gas down the intake

do you mean to disconnect the engine side fuel hose from the pump and pour gas directly into there? Or can I access the fuel line at the other end nearer the engine somewhere, just before the injectors?

I think our model has a connector like this engine-side, did you mean access this?

https://imgur.com/a/w98HxAS

Like I said, although I've done quite a lot of my own repairs over the years, I'm not a super-experienced mechanic, and I don't have a Haynes for this car which is making everything doubly difficult.

I really appreciate the advice... like I said, I'm sry to be dense.

24th August 2021, 17:14

Quote:

Originally Posted by MartinObviously

the relay under the ECU controls EVERYTHING.

Fuel pump,injectors, feed to the coil pack.

If the relay is giving power to the coil pack, it's also giving the fuel pump power.

If the fuel pump isn't turning, either the earth is faulty, a wire is broken on the pump has simply died.

Just to confirm it is a fuel problem, pour some petrol/gas down the intake. A good 100ml or so and start the car. If it runs "normally" then 100% the fault is with fuel delivery.

Urgent Update : I managed to borrow a multimeter but the damn car has been towed. I'm going to the impound lot tomorrow and going to test the pump connector.

If I find a normal 12Vish charge going to the pump is it a reasonable conclusion that the pump is simply dead?!

If so I can go look for a new pump and hopefully change it at the pound.

Thanks!

24th August 2021, 17:44

Quote:

Originally Posted by MartinObviously

the relay under the ECU controls EVERYTHING.
pour some petrol/gas down the intake. A good 100ml or so and start the car

Sry to be ignorant, Martin... but I'd like to check this too if possible.

When you say pour some gas down the "intake" - do you mean disconnect the engine hose from the fuel pump and pour fuel directly into the hose itself... or by "intake" are you referring to something else at the other end of the hose in the engine itself? If so, where can I find that?

Thanks for your help!

25th August 2021, 11:10

I meant to put a little bit of petrol down the throttle body right at the engine, half a cup, if it runs it will just confirm that the problem is fuel supply.

However since you mention it, if you see 12v at the fuel pump connector, then that would suggest the problem is the fuel pump itself.

Sorry to hear you car is impound

25th August 2021, 18:04

Quote:

Originally Posted by MartinObviously

I meant to put a little bit of petrol down the throttle body right at the engine, half a cup, if it runs it will just confirm that the problem is fuel supply.

However since you mention it, if you see 12v at the fuel pump connector, then that would suggest the problem is the fuel pump itself.

Sorry to hear you car is impound

I had no idea you could even do that... I'm not even sure how to access on this car. Looking at the photos I'm guessing it could be this bit here - I think that's the throttle body behind there - it's hard to tell. Can I just screw that cap off and throw a small cup of gas in there? I might try that tomorrow if I have the time.

https://imgur.com/a/Z3ThvxJ

I tested the connector to the battery this morning and it's definitely getting power... it fluctuated a bit but I think the battery is getting very low, but it definitely hit 12v on turnover. I didn't dare turn it over for too long, think I've only got a couple more starts before battery is empty.

Thanks again for the help!

26th August 2021, 13:27

Quote:

Originally Posted by gulli

I had no idea you could even do that... I'm not even sure how to access on this car. Looking at the photos I'm guessing it could be this bit here - I think that's the throttle body behind there - it's hard to tell. Can I just screw that cap off and throw a small cup of gas in there? I might try that tomorrow if I have the time.

https://imgur.com/a/Z3ThvxJ

I tested the connector to the battery this morning and it's definitely getting power... it fluctuated a bit but I think the battery is getting very low, but it definitely hit 12v on turnover. I didn't dare turn it over for too long, think I've only got a couple more starts before battery is empty.

Thanks again for the help!

No not there, that it is the crank case breather

Don't worry about it, I think the problem is your fuel pump if you measured 12v at the fuel pump connector when turning over.

27th August 2021, 18:40

Quote:

Originally Posted by MartinObviously

No not there, that it is the crank case breather

Don't worry about it, I think the problem is your fuel pump if you measured 12v at the fuel pump connector when turning over.

Yeah, I realized it wasn't right when I went back and looked at the car itself!

However I've discovered the problem is DEFINITELY ELECTRICAL.

I hooked the pump up directly to the battery and the car started first time. It seems the problem is that an uneven voltage is reaching the pump. I couldn't test it very long before because the battery was getting so low.

I will test it better once I have been able to run the engine and charge the battery up more - but what I THINK is happening is when I turn the ignition the voltage is seriously fluctuating and dropping from 12V down to 8V. But this is where I am really lost. I've been looking at this diagram for the last hour or more... I can see it gets its power through the Fuel Injection Main Relay but I can't tell if anything else could be affecting it.

Here is a wiring diagram where I've marked off the path as far as I can understand it -

https://imgur.com/a/IZV6Zsf

I think this is the main fuel injection relay in the engine -

https://imgur.com/a/ADPf7Ms

What I'd really like answered is the following :

Given there is definitely some power getting through to pump I assume it can't be an earthing problem - so is the main fuel injection relay the most likely source of the problem?

If the problem isn't the relay then the most likely other culprit seems to be the ECU itself... could that be the problem or is there ANYTHING else which could be causing the problem?

I know I've been asking a lot, I really appreciate the replies you've been a great help.

Thanks so much for everyone who has already answered here - hopefully I am getting closer to a solution... but electrics is where I really start to get lost - I so hope I can just get a new relay unit and plug it in.

27th August 2021, 18:41

Quote:

No not there, that it is the crank case breather

Don't worry about it, I think the problem is your fuel pump if you measured 12v at the fuel pump connector when turning over.

Yeah, I realized it wasn't right when I went back and looked at the car itself!

However I've discovered the problem is DEFINITELY ELECTRICAL.

I hooked the pump up directly to the battery and the car started first time. It seems the problem is that an uneven voltage is reaching the pump. I couldn't test it very long before because the battery was getting so low.

I will test it better once I have been able to run the engine and charge the battery up more - but what I THINK is happening is when I try the ignition the voltage is seriously fluctuating and dropping from 12V down to 8V.

But this is where I am really lost. I've been looking at this diagram for the last hour or more... I can see it gets its power through the Fuel Injection Main Relay but I can't tell if anything else could be affecting it.

Here is a wiring diagram where I've marked off the path -

https://imgur.com/a/IZV6Zsf

I think this is the main fuel injection relay in the engine -

https://imgur.com/a/ADPf7Ms

What I'd really like answered is the following :

Given there is definitely some power getting through to pump I assume it can't be an earthing problem - so is the main fuel injection relay the most likely source of the problem?

If the problem isn't the relay then the most likely other culprit seems to be the ECU itself... could that be the problem or is there ANYTHING else which could be causing the problem?

I know I've been asking a lot, I really appreciate the replies you've been a great help.

Thanks so much for everyone who has already answered here - hopefully I am getting closer to a solution... but electrics is where I really start to get lost - I so hope I can just get a new relay unit and plug it in.

28th August 2021, 11:59

Oh I thought you had 12v under load!

Voltage is dropping with load?

It could be corrosion/dirt on the fuse causing a resistance. Remove it and clean the contacts.

Check the continuity/resistance of the wire from pin 9 on your main injection relay and Fuse 9, then from fuse 9 to pin 2 on your fuel pump. Resistance should be very low of course.

The earth for the fuel pump is on the C pillar next to the seat belt reel for the rear seat. Thats your passenger side. Sometimes they can rust here.

Remember the same power wire, feeds your coil pack as well!! so if it runs smooth then I can't think that it is a supply issue within the relay. Pin 1 (coil pack) and 9 (feed to fuel pump and O2 sensor) are both fed from the supply into pin 11.

I'm not sure about your small relay, we do not have manifold heating in the UK so I've never seen one.

1st September 2021, 14:49

Quote:

Oh I thought you had 12v under load!

Voltage is dropping with load?

It could be corrosion/dirt on the fuse causing a resistance. Remove it and clean the contacts.

Check the continuity/resistance of the wire from pin 9 on your main injection relay and Fuse 9, then from fuse 9 to pin 2 on your fuel pump. Resistance should be very low of course.

The earth for the fuel pump is on the C pillar next to the seat belt reel for the rear seat. Thats your passenger side. Sometimes they can rust here.

Remember the same power wire, feeds your coil pack as well!! so if it runs smooth then I can't think that it is a supply issue within the relay. Pin 1 (coil pack) and 9 (feed to fuel pump and O2 sensor) are both fed from the supply into pin 11.

I'm not sure about your small relay, we do not have manifold heating in the UK so I've never seen one.

Thanks for the detailed advice - sry didn't reply sooner, took a break. I'm going out to the car this afternoon and hopefully will get some better readings - last time the battery was so low and I was doing it by myself.

I'll try to get the readings you mentioned. I assume I can earth those directly to the battery itself to complete the circuit.

When I first checked the car the fuses were one of the first things I looked at and I even switched out the fuse in slot 9 with another 10amp fuse. They looked clean.

When I was running the car the other day it managed to start and run fine just with the live wire connected to the battery... so I don't think it's the earth which is causing the problem.

Now I've managed to charge the battery up a bit I can test a bit better. Hopefully I'll have some more info later.

Thanks again. Will post back soon.

2nd September 2021, 10:03

There might be a couple of duplicate posts that now appear above, dont know why but the spam bot filter picked on a couple of your posts which i have approved now so it shouldnt happen again

3rd September 2021, 20:15

Quote:

There might be a couple of duplicate posts that now appear above, dont know why but the spam bot filter picked on a couple of your posts which i have approved now so it shouldnt happen again

Thank you. I think that was partly my fault. I tried to post something and it didn't go through so I went back and posted it again... the 2nd time I saw a message about it being held back for moderation, I'd missed it the first time.

However I've noticed on this forum when I quote someone directly (with their =<name>;IDNUMBER) it always seems to hold the comment back for moderation. Dunno if that's intentional or a bug but it discourages quoting people.