Technical Multijet no start.

[koalar]

For over a week I have been saying you got to start somewhere

A Jag, a Merc and so on is not a panda multijet

Even within the multijet range some are GM designed and some fiat

The only thing that's important is the 1.3 multijet

At a minimum of 200 rpm the fuel pressure should be 300 bar after 5 seconds

How hard can it be to test, all you have to do is prevent the car from starting, which a one point it wasn't doing that any rate


Ramp up is normally 3/4 of a second, I have never tested a 1.3 multijet, which might be different

I would not expect 62 at 234 rpm
And 126 bar at 722 rpm

If you take the pressure regulator off the rail you are supposed to replace the seal, probably not strictly necessarily, who knows

 

[DaveMcT]

The video shows pressure getting up well within 5 seconds. The question is how do you get it to crank but not fire the injectors?Unplugging them stops anything happening.

 

[bugsymike]

The video shows pressure getting up well within 5 seconds. The question is how do you get it to crank but not fire the injectors?Unplugging them stops anything happening.

Just a guess , but would disconnecting the crank sensor plug do that?
I liked the video of a simple test of the regulator involving no expensive equipment.

 

[DaveMcT]

Testing the pressure regulator for leak-off is awkward because the line back to tank has a tee joint. I will need a plug to close that. A cut off bolt and zip tie to hold it in should do it. A job for tomorrow.

Pressure sensor fuel end is spotless as is the wiring end. It runs at high pressure so testing it off the car unlikely to show anything. Testing in situ will need insulation piercing meter probes. Another cost.

A new Bosch sensor is £40 so might be worth a punt. I’m not convinced it’s broken.

The pressure regulator looks like £150 upwards. Who knows if the cheap(er) ones are any good. I’m not throwing parts at that without evidence. Though steep pressure drop on every significant throttle press is stacking up the evidence.

I’ve just run another test but started the graph with engine running.
Idle (800rom) = 380 bar.
It sits between 350 and 750 at light throttle. Every time gas pedal goes down to accelerate normally, the fuel pressure drops. MES shows max pressure 1142 bar. Min pressure 158. It trips the warning light on the first throttle down and pressure drops to 158 (min recorded) on every useful pedal press.

I’m thinking fuel pressure control valve is the problem. It has 136,000 miles. Pump has just 7000 miles. Repeated test drives have triggered the same fault. It was ok for a mile or two. It’s now on every throttle press.

I’ve also posted the numbers on top of control valve.

 

[DaveMcT]

How hard can it be to test, all you have to do is prevent the car from starting, which a one point it wasn't doing that any rate

I would agree but no ECU = no data.

How do I get the engine to turn on its starter but stop the injectors triggering, while keeping the ECU powered up?

 

[bugsymike]

Testing the pressure regulator for leak-off is awkward because the line back to tank has a tee joint. I will need a plug to close that. A cut off bolt and zip tie to hold it in should do it. A job for tomorrow.

Pressure sensor fuel end is spotless as is the wiring end. It runs at high pressure so testing it off the car unlikely to show anything. Testing in situ will need insulation piercing meter probes. Another cost.

A new Bosch sensor is £40 so might be worth a punt. I’m not convinced it’s broken.

The pressure regulator looks like £150 upwards. Who knows if the cheap(er) ones are any good. I’m not throwing parts at that without evidence. Though steep pressure drop on every significant throttle press is stacking up the evidence.

I’ve just run another test but started the graph with engine running.
Idle (800rom) = 380 bar.
It sits between 350 and 750 at light throttle. Every time gas pedal goes down to accelerate normally, the fuel pressure drops. MES shows max pressure 1142 bar. Min pressure 158. It trips the warning light on the first throttle down and pressure drops to 158 (min recorded) on every useful pedal press.

I’m thinking fuel pressure control valve is the problem. It has 136,000 miles. Pump has just 7000 miles. Repeated test drives have triggered the same fault. It was ok for a mile or two. It’s now on every throttle press.

I’ve also posted the numbers on top of control valve.

It does keep suggesting regulator problems in that direction, however given the cost involved a conclusive test is understandable.

 

[koalar]

I would agree but no ECU = no data.

How do I get the engine to turn on its starter but stop the injectors triggering, while keeping the ECU powered up?

I don't understand

It's reads the pressure without cranking, disconnect the crank sensor, block the air intake, download some diagnostics that actually works

Put a pressure gauge on

I been asking for over a week, the car wasn't even starting then and could be read directy

We messed about with everything else, without doing the basics

The only graph we have got shows desired and actual pressure match even the big dips, there's just a 2 seconds lag before the actual catches up

The pressures look terrible 62 at 234 rpm and 126 bar at 722 rpm


Whether it's leaking off
Whether the pressure sensor is reading wrong
Whether the pump isn't supplying quick enough
Whether an injector is leaking
Whether the pressure release valve is faulty
Whether MES is giving the wrong information

Is anybodies guess

If it was me, the worst case and I had to borrow a pressure gauge

Within a few hours I would know, what the pressure is at the common rail, what the pressure the pump supplying, how quick the pump is supplying, and if needed if an injector has excessive leak by

 

[DaveMcT]

I still do not know how to get it to crank and supply its normal pressure.
A diesel pressure test kit with 2000 bar gauge and adapters to “break into” and injector line costs £200. I can replace pump, regulator and sensor for £300.

The engine runs smoother than it ever has and it starts without smoke. A poor performing injector is possible but highly unlikely.

 

[koalar]

When first asked the engine wasn't even running

All that was asked for was the pressure while cranking and the rpm

We need something that's known

Even now it's starting it still reading 90 psi at 0 rpm

Disconnect the crank sensor signal it can't fire

And give the psi and rpm

You can read the voltage directly from the sensor with a volt meter but really you shouldn't need to

Or use different software

 

[DaveMcT]

The Alfa software won’t even connect without paying. That’s unacceptable to me. It should at least allow basic operation to allow a useful evaluation of it’s capabilities.

 

[DaveMcT]

Today I’ve done some leak down tests.

Injectors leak off sent to a bottle. Hose barb capped at pressure control valve banjo.

Pressure Regulator outlet sent to a bottle.

Fuel pump leak off capped at regulator and flow fed into a large bottle. That shifted nearly a litre of fuel in 30 seconds of idling. It has a large bore hose (8mm) so maybe it’s normal. Ive redirected it back to the tank.

Engine starts easily (no glow plugs atm). Rail pressure regulator valve was running a continuous flow and clearing air. When that settled there was a continuous flow similar to all four injectors. Revving the engine with a firm kick did not trip the ELM warning light. Regulator flow stayed the same. When engine switched off regulator flow stops. No-obvious dribble when engine off. Obviously I can’t drive with tubes dribbling into bottles.

My suspicion is the pressure regulator is passing too much fuel. Should it pass any fuel at light load?

 

[DaveMcT]

Latest data traces.

Cranking with glow plugs removed (surprisingly easier than getting to the crank sensor).

Fuel pressure shoots up and stays stable. Expected and actual pressures follow pretty well. Stabbing the throttle pedal has no meaningful effect.

 

[DaveMcT]

Another run with the glow plugs back in. Engine started and revved. Minimal fuel gets added at no load so the problem never happens. A short drive afterwards confirms the problem has not changed. Immediate EML and cough when you put the accelerator down.

During the short period of this and the previous test, I got 80ml from the injectors leak off and 300ml from the rail pressure regulator. Does this look normal?

I will do individual injectors but waiting on brass leak-off plugs. I’m expecting the OEM plastic to have gone brittle.

 

[koalar]

Looks well short of 300 bar at 200 rpm @ 5 seconds to me

But then again it looks like the injectors are firing causing the dip down

 

[DaveMcT]

Thanks Koalar.

I did this with glow plugs removed. I’ll have to pull things apart to disconnect the CPS and repeat the test.

Do you think the control valve leak rate is normal? I mean if the pump is weak the valve will return less to the tank. But if valve is weak it will return too much to the tank. Is there flow rate at idle which can indicate an issue?

Tomorrow I’ll will get individual injector leak off rates. I’ve thought up a way to do it with the kit I have.

 

[koalar]

I don't know

Each system is different, I not had the fiat 1.3D or done any testing on one

I have worked on similar Bosch pumps and the rise time is normally around 1/2 second, you have 8x that

Have to think how to move forwards with what we have,


Having a valve in the system, and not knowing how it being controlled, limits the understanding of any graph

For example a working system and 30% duty cycle, could look the same system with a small leak and a 60% duty cycle

 

[DaveMcT]

I’ve just ordered a new valve. If the pump is faulty the replacement will at least have a good control valve to work with.

I’ve not bought a new pressure sensor as this one responds quickly. But when I’ve done the parts compatibility checks I’ll probably get one as well.

 

[koalar]

Are you sure multiECUscan is reading right

200 rpm with the heater plugs out does not sound right

Time scale across the bottom is in seconds I take it, otherwise I been talking rubbish

 

[DaveMcT]

it’s hard to be really accurate but MES matched up with the dash for engine speed. Idle is 1100 cold dropping to 800.

The 300 ml dumped by the PCV when all four injectors spilled 80ml seems a lot for the high pressure side to lose. It has done 130,000 miles. Hence the new valve. It’s cost £102 and the seller confirmed the etched label numbers are correct.

A lot of air came out (the leak-off side had been opened) but the odd stray bubble carried along at the same rate.

My road test last night initially felt normal. It scooted away with a firm pedal push. 1/4 mile further along, it did the usual trip on low fuel pressure. MES showed the usual down-spike with throttle.

 

[bugsymike]

A lot of air came out (the leak-off side had been opened) but the odd stray bubble carried along at the same rate.

Strange air bubbles in high pressure common rail area after testing for a while, should have cleared, (has to affect injection), no logical reason why?