Hesitancy on acceleration - fuel pump?

[NickUK]

Here's another technical question from me before I spend more money doing up my Z3...

My car has been either hesitant / jumpy or just very slow to accelerate on a few occasions. It's not all the time but I'd put my foot down and the car would struggle to move and then start working further down the road. It can happen on one journey a few times and then be fine for 1000 miles.

With it being a now and again thing and based on experience, I am thinking it's the fuel pump because the car is high mileage. I have similar symptoms with the LPG system on my Volvo - when it is under fuelling at low revs, the car is jumpy.

Before I go out and buy a fuel pump, I thought it would be worth gathering any thoughts from the experts, you. I was thinking of buying this fuel pump by the way: https://www.eurocarparts.com/p/pwm-fuel-pump-441720021. I have seen others on eBay for £15 but assuming they are made from plasticine.

Thanks.

 

[t-tony]

Have you had a code reader on the car before doing anything Nick. It could possibly be the inlet camshaft position sensor starting to fail. It doesn’t always trigger the engine management light.

Tony.

 

[NickUK]

Have you had a code reader on the car before doing anything Nick. It could possibly be the inlet camshaft position sensor starting to fail. It doesn’t always trigger the engine management light.

Tony.

I haven't but dread to think what will come up! There's an OBDII socket under the dash isn't there? I have a phone app based code reader that will plug into that.

 

[Delk]

I only had one fuel pump start to fail on a fuel injected car. When it happened the pressure would drop and you would loose all power since the injectors were not working. It wasn't a hesitation or stumble it was a full loss of power. And when you were driving down the motorway it was really bad.

 

[NickUK]

I only had one fuel pump start to fail on a fuel injected car. When it happened the pressure would drop and you would loose all power since the injectors were not working. It wasn't a hesitation or stumble it was a full loss of power. And when you were driving down the motorway it was really bad.

Thinking about it, mine was more a loss of power. I'm confusing the symptoms with my other car. It was more like the car only had 20bhp as I put my foot down to the floor. I suppose whatever it is will hopefully show with a read of fault codes anyway.

 

[t-tony]

I haven't but dread to think what will come up! There's an OBDII socket under the dash isn't there? I have a phone app based code reader that will plug into that.

You will probably have yo if into the round socket under the bonnet to access the codes on the motor Nick.
You will need an adapter cable to do this.

Tony.

 

[Stevo7682]

Blocked or partially blocked fuel filter could also give similar symptoms.
As @t-tony has said obd2 under dash gives limited access you need to use the 20 pin obd plug under the bonnet
So if you get a code reader you will still need a 16 to 20 obd lead to allow you to access all a systems

 

[mrscalex]

Blocked or partially blocked fuel filter could also give similar symptoms.
As @t-tony has said obd2 under dash gives limited access you need to use the 20 pin obd plug under the bonnet
So if you get a code reader you will still need a 16 to 20 obd lead to allow you to access all a systems

Not sure if the pre-facelift cars have the square dash connector anyhow?

 

[NickUK]

Not sure if the pre-facelift cars have the square dash connector anyhow?

I'll just buy an adapter as they are only £5.

 

[jonco]

I'll just buy an adapter as they are only £5.

Nick - if you are stuck then I have 20 pin adaptor and WIFI units. Also INPA loaded on an old windows laptop (may need to raise some steam to run it).
However, I recall your mileage was 150k plus so I would be looking at fuel filter first as already suggested. Pic is mine at ~70k.

 

[NickUK]

Nick - if you are stuck then I have 20 pin adaptor and WIFI units. Also INPA loaded on an old windows laptop (may need to raise some steam to run it).
However, I recall your mileage was 150k plus so I would be looking at fuel filter first as already suggested. Pic is mine at ~70k.View attachment 122897View attachment 122901

Yes it's high mileage. I'll change that first then. Thanks.

 

[t-tony]

Fuel filter is certainly one item which gets over looked as they're not the easiest to do unless car is lifted on ramp etc.

Tony.

 

[t-tony]

Do the ASC and ABS lights all work ok?

Tony.

 

[jonco]

..................... they're not the easiest to do unless car is lifted on ramp etc.......

Actually not too bad on the Z3 Tony - did mine on stands. The actual mounting is close to the side sill.

 

[t-tony]

Easy enough to someone with a bit of idea Colin but not so much for a novice. Plus with the cover over it many people would not realise it was there.

Tony.

 

[IainP]

When I did mine , I discovered the filter and pipes had been fitted with all the clips pointing upward, no way to easily loosen them. By releasing the retaining clamp I found I could press the filter down and have sufficient room for a 1/4" socket held in vice grips to loosen the clamps enough to rotate them for proper access.

Also, if you still have hesitation problems after the filter is changed, you may have a small amount of water in the fuel tank. Even 2-3 tablespoons of water, from condensation etc, can cause momentary hesitation at times. Add 250-500 cc of Methanol to a low tank, give it a good slosh, then fill the tank. The Methanol combines with the water allowing it to mix with the fuel.