Technical Fiat Grande Punto - Crank but no start

[Bartoosh]

2006 Fiat Grande Punto 1.2 Active that cranks but won't start. The car used to start on the button but now it just turns over without firing. I'm trying to diagnose the issue so I don't go down the road of replacing parts that are healthy.

What I've checked so far:
(1) Fuel Gauge. There's a quarter of a tank of petrol in the fuel tank.
(2) Immobiliser. When I turn the key to ignition 1, the padlock light goes out after a second or two.
(3) Earth cables. All present and correct though it's difficult to gauge internal condition. I ran a jump lead from the battery to the engine but this made no difference.
(4) Battery. Healthy voltage (which I expected given the engine turns over well).
(5) RPM counter. When I try to start the car, the RPM needle moves slightly.
(6) Spark plugs. They look healthy, the gaps are good, and they all spark. This, I assume, rules out any issue with the spark plugs or ignition coils.
(7) Fuel pump relay. I swapped this with the horn relay and the horn still works suggesting that the fuel pump relay is operating ok. After swapping the relays the engine still cranks but won't start.
(8) Fuel pump. When I turn the key to ignition 1, I hear a whirr from the fuel pump which suggests it's engaging. However, I'm not convinced that the fuel pump is working properly and feel more extensive testing is required.
(9) Throttle body. It's clean and I can manoeuvre the butterfly by hand. When I turn the key to ignition 1, the throttle body whirrs and the butterfly briefly opens slightly before closing. There is no further movement. Again, this isn't an extensive test and I appreciate any tips on how to determine if it's working properly.
(10) Diag tool. This revealed no fault codes.

I did manage to get the car started once but after 50 yards of driving the engine conked out. Since then it won't fire up at all.

Can you lovely folk recommend more tests? I feel like I can rule out no spark, but no fuel is still a possibility.

I used a basic bluetooth diag tool to check fault codes and this returned nothing. I have since acquired Multiecuscan so I will check for fault codes again. Are there some tests that I can run with MultiECUscan to check components (like the fuel pump, injectors, pressure rail, throttle body, and ecu)?

Can I also use MultiECUScan to check the sensors? Frankly, I'm confused by the role the crank/cam/MAP/air/temp sensors play and how to track communication.

Are there any hoses that could potentially affect starting (e.g. vacuum/breather hoses)?

Many thanks in advance for any assistance.

 

[GrandePunto PL]

Fuel pressure - top 3 easiest measurements in those cars (other 2 are intake vacuum and oil pressure).
You check it at the pump (easier than in the engine bay, fuel rail, unless you have specialized connector, adapter).
Clamp a hose or pneumatic quick connector 8 mm. Should be 3,5 bar.
One o-ring can prevent the car from starting. Pressure relief valve.

MES has most tests. You can command many things, ON/OFF.
Sensors too, at least before and after start. Not so much during cranking (communication can be lost due to voltage drop).
That's why real Pros use oscilloscope! https://www.youtube.com/c/AutomotiveTestSolutions/videos No parts swapping.

 

[AnthonyH]

Can you bump start the car?

Can you swap the battery for a known good one?

 

[Bartoosh]

Can you bump start the car?

Can you swap the battery for a known good one?

I have 2 healthy batteries. I tried both; same result.

 

[Bartoosh]

Update:

I attached a fuel pressure gauge to the schrader valve on the fuel rail and turned the key in the ignition. There is absolutely no fuel pressure whatsoever.

I then sprayed some easy start into the throttle body. The car started, ran for a few seconds, then conked out. I did this again, it started again.

Given that we have a spark but no fuel pressure, this is looking very much like a no fuel issue to me.

I suspect that the fuel pump is faulty but, before buying the part, I'd like to rule out the following:
(1) The vehicle is equipped with a fuel cut off switch. It's never been in an accident but I pressed this anyway to make sure it hasn't been engaged. I heard no click and it made no difference. Can I safely rule out the fuel cut off switch?
(2) Are there any tests that I can run (perhaps with MES) to determine whether the fuel pump is being told to engage by the ECU?

 

[AnthonyH]

Have you checked the fuel filter, maybe its blocked?

 

[Bartoosh]

Have you checked the fuel filter, maybe its blocked?

Is the fuel filter part of the pump assembly on the Grande Punto?

 

[AnthonyH]

I think it depends on the exact model, some have them in the engine compartment, mine aren't so probably on the tank, or elsewhere.

 

[GrandePunto PL]

You claimed (at point 8), that you can hear the fuel pump priming before start. So the motor is working.
Yes, you can command pump ON via MES.
Zero pressure is not possible (it should pump something, at least half bar or 1), are you sure you have proper connector/adapter, that opens the valve on the rail?
Besides that, told you to do the measurement at fuel pump - it's easier (no special adapters needed)!
Plus, my picture (relief valve, o-ring failure - check this).

 

[Bartoosh]

You claimed (at point 8), that you can hear the fuel pump priming before start. So the motor is working.
Yes, you can command pump ON via MES.
Zero pressure is not possible (it should pump something, at least half bar or 1), are you sure you have proper connector/adapter, that opens the valve on the rail?
Besides that, told you to do the measurement at fuel pump - it's easier (no special adapters needed)!
Plus, my picture (relief valve, o-ring failure - check this).

Yes, I can hear the fuel pump priming when I turn the key to ignition 1. However, according to the documentation I've read this just means that power is being drawn. It doesn't necessarily mean that the pump is successfully sending fuel.

That being said, I wasn't convinced that the fuel pressure gauge was opening the valve on the rail as I had to use an adapter. I will try testing pressure at the fuel pump, as suggested. Where is the best place to connect the fuel pressure gauge? Do I disconnect the fuel supply line from the top of the pump and connect the fuel pressure gauge here?

With respect to your picture, where is this pressure relief valve located?

 

[Bartoosh]

I've lifted the rear seat and removed the plastic cover to reveal the top of the fuel pump. It was very dirty in there which leads me to believe that it's the original pump. I had to give the area a gentle clean before testing fuel pressure.

 

[GrandePunto PL]

Outlet should be 8 mm, you connect there whatever you have (piece of hose etc.) available.
Relief valve/regulator may look different (there are multiple variations of the pumps - but function blocks are the same).
Look for "thing" attached to the filter (between filter and actual pump). Probably it will have a clip (or two) to undo.

 

[Bartoosh]

UPDATE: I connected a hose and a fuel pressure gauge to the fuel supply line at the top of the fuel pump. When I turn the ignition to position 1, the pump does send some fuel but pressure is only 0.5 BAR.

 

[Bartoosh]

SOLVED.

I replaced the fuel pump and the car now starts on the button. I ran the car for a while and it settled nicely with no leaks.

Many thanks to those who provided assistance, particularly @GrandePunto PL for his detailed advice and excellent guide which can be found here:

Fuel pump check or replacement. [1,4 8V]

Fuel pump in the petrol engine should make 3,5 bar (little drop is acceptable, like 0,1-0,2 bar, no problem - it must be serious drop to cause problems, like a half or full 1 bar). Pressure on the rail in the engine bay, in theory. But you can...

www.fiatforum.com

For those tasked with replacing a fuel pump on a Fiat Grande Punto, I can also recommend the following video by Haynes Manuals:


Having just completed the job myself, I can provide the following tips:
(1) It can get very dirty in the fuel pump enclosure so make sure you clean the area before you remove the fuel pump to avoid contaminating your fuel.
(2) The fuel pump lock ring was locked tight on my vehicle and was virtually impossible to remove undamaged without the proper tool. These are pretty cheap online and worth the investment IMHO as it saves time and hassle.
(3) All guides recommend replacing the O-Ring rubber gasket that seals the lock ring. Be careful when ordering. I ordered a 3rd party O-Ring from an online retailer who claimed that it was compatible only to find out that it was too small. I had to buy another to complete the job.