2.0 JTS Fuel Problem
G
12342
16
2.0 JTS. Mk 2 facelift on a 53 plate, the odo says its done 53k miles but the management thinks its done 80k….Bought from an auction as a runner.
Unfortunately, it isn’t. It’ll start, idle and even rev cleanly, but not for long. It’ll suddenly loose all will to run and splutter to a stop. From cold, best case scenario for this to happen is around 5 minutes.
A friend, Mark, has been given the task of finding the problem.
Mark’s diagnostic kit has identified the problem as low fuel pressure. JTS’s are direct injection. Fuel is pumped from the fuel tank by an Electric Pump at 5.5bar to a high pressure pump that’s driven off the exhaust camshaft. The high pressure (HP) pump then ups the pressure to between 50 and 120 bar depending on engine load and speed.
The pressure isn’t controlled by the pump. There is a pressure sensor and a solenoid that opens and closes a regulator in the HP fuel rail. Excess pressure/fuel is dumped back into the low pressure feed from the electric pump in the tank.
Essentially, the electric pump provides a large volume of fuel under modest pressure. The HP pump is like a pressure washer. It doesn’t increase the volume of fuel going in, in fact the small bore pipes on the HP side limit volume, it just ups the pressure. Its like the difference between running a pressure washer with the end of the lance on (high velocity, will strip paint) and with it off (limp wristed, nothing for the pressure to act against….)
The engine management has set values for pressure that it aims to meet by opening and closeing the fuel pressure regulator. We know this because the diag kit mark has shows the pressure the management is trying to achieve and also has a realtime readout of the actual pressure.
So if you start the engine, everything is fine. Good fuel pressure for a minute or two - At idle it should be around 50bar.
Then over the space of 10seconds or so the pressure drops sharply to 5.5bar and the engine dies.
So far, this is what has been replaced:
Fuel pressure regulator on the HP side
Fuel pressure sender
Electric pump in the fuel tank (LP side)
That lot, by all accounts wasn’t cheap and in the face of mounting costs – parts as well as labour, the car’s owner will not spend any more money on it without knowing it will cure it. Mark is already out of pocket because he’s has to pay for the regulator and he’s spent hours, unpaid, trying to find the problem. I think because its become a challenge, he refuses to give up.
The regulator solenoid acts like a switch, its either open or shut with no leeway in between. Last night we hooked up a switchable 12v feed to it and stated the engine. As you’d expect when it was shut, FP would climb and when it was open FP would drop.
But here’s the weird thing. Even with the regulator wide open and FP down to an indicated 5.5bar, the engine would still idle perfectly normally apparently running on pressure provided solely by the electric pump in tank.
And when it did decide to play games, we tried holding the regulator shut but FP still dropped and the engine died.
So where the hell is the fuel pressure going?!!! There are no obvious leaks on the HP side. It happens more readily when the engine is warm. The plugs are black as the ace of spades but that could be attributed to the engine only being able to run when its cold so it will be being over fueled.
Grasping at straws, on the basis there could be crud in the system between the HP pump and the regulator, I suggested that we take the regulator out and turn it over.
Turning the engine over resulted in fuel going everywhere, obviously, the in tank pump saw to that. But the hole in which the regulator sits had air bubbling out of it for 10minutes or so after we had turned the engine off…. Is this a red herring or is there an air leak?
Any Ideas?
Unfortunately, it isn’t. It’ll start, idle and even rev cleanly, but not for long. It’ll suddenly loose all will to run and splutter to a stop. From cold, best case scenario for this to happen is around 5 minutes.
A friend, Mark, has been given the task of finding the problem.
Mark’s diagnostic kit has identified the problem as low fuel pressure. JTS’s are direct injection. Fuel is pumped from the fuel tank by an Electric Pump at 5.5bar to a high pressure pump that’s driven off the exhaust camshaft. The high pressure (HP) pump then ups the pressure to between 50 and 120 bar depending on engine load and speed.
The pressure isn’t controlled by the pump. There is a pressure sensor and a solenoid that opens and closes a regulator in the HP fuel rail. Excess pressure/fuel is dumped back into the low pressure feed from the electric pump in the tank.
Essentially, the electric pump provides a large volume of fuel under modest pressure. The HP pump is like a pressure washer. It doesn’t increase the volume of fuel going in, in fact the small bore pipes on the HP side limit volume, it just ups the pressure. Its like the difference between running a pressure washer with the end of the lance on (high velocity, will strip paint) and with it off (limp wristed, nothing for the pressure to act against….)
The engine management has set values for pressure that it aims to meet by opening and closeing the fuel pressure regulator. We know this because the diag kit mark has shows the pressure the management is trying to achieve and also has a realtime readout of the actual pressure.
So if you start the engine, everything is fine. Good fuel pressure for a minute or two - At idle it should be around 50bar.
Then over the space of 10seconds or so the pressure drops sharply to 5.5bar and the engine dies.
So far, this is what has been replaced:
Fuel pressure regulator on the HP side
Fuel pressure sender
Electric pump in the fuel tank (LP side)
That lot, by all accounts wasn’t cheap and in the face of mounting costs – parts as well as labour, the car’s owner will not spend any more money on it without knowing it will cure it. Mark is already out of pocket because he’s has to pay for the regulator and he’s spent hours, unpaid, trying to find the problem. I think because its become a challenge, he refuses to give up.
The regulator solenoid acts like a switch, its either open or shut with no leeway in between. Last night we hooked up a switchable 12v feed to it and stated the engine. As you’d expect when it was shut, FP would climb and when it was open FP would drop.
But here’s the weird thing. Even with the regulator wide open and FP down to an indicated 5.5bar, the engine would still idle perfectly normally apparently running on pressure provided solely by the electric pump in tank.
And when it did decide to play games, we tried holding the regulator shut but FP still dropped and the engine died.
So where the hell is the fuel pressure going?!!! There are no obvious leaks on the HP side. It happens more readily when the engine is warm. The plugs are black as the ace of spades but that could be attributed to the engine only being able to run when its cold so it will be being over fueled.
Grasping at straws, on the basis there could be crud in the system between the HP pump and the regulator, I suggested that we take the regulator out and turn it over.
Turning the engine over resulted in fuel going everywhere, obviously, the in tank pump saw to that. But the hole in which the regulator sits had air bubbling out of it for 10minutes or so after we had turned the engine off…. Is this a red herring or is there an air leak?
Any Ideas?
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Chris155,
Did you ever manage to solve the fuel pressure problem? Could the loss of pressure be due to a faulty high pressure pump?
Did you ever manage to solve the fuel pressure problem? Could the loss of pressure be due to a faulty high pressure pump?
G
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·The pump was replaced, the fault never found.
Joined
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120 Posts
I have the same problem with my 159 2.2JTSThe pump was replaced, the fault never found.
I have replaced the pump in the tank. Pressure from it is normal, but engine still has lack of power and more I press an accelerator, engine performance gets worse and at last it stops, unless I release the accelerator pedal.
In the morning, engine starts with hesitation and 2000rpm (instead of 1200rpm) and after 10-15 seconds warm up, 1200rpm. After approximately 1 minute - usual/normal 800rpm.
I'm driving like a turttle! Slightly touching accelerator pedal with fear! If I press accelerator a bit much, engine loses power and I can stik in the traffic...
WHAT A HELL THAT CAN BE???
Has anyone got any further experience with this type of issue?
My son's 156 JTS cut out completely earlier in the week and the symptoms are very similar except it won't even start.
No ECU faults.
Crank sensor is good ( checked by resistance, oscilloscope and FiatECUScan when cranking on the starter )
Engine is mechanically fine ( checked the cam timing with cam locks just to be sure and did a compression test )
Fuel pressure regulator operates when hooking it to +12v
Fuel gushes out of the hose when disconnected from the high pressure pump ( so low pressure pump is probably good )
Fuel pressure sensor reports 5.5 bar when cranking the engine in FES ( about right for the low pressure pump )
It is unlikely to be the ignition side or injectors - all would have had to fail at exactly the same time. There is no evidence of any cylinder firing.
I did get the engine started very briefly yesterday when I disconnected the fuel pressure regulator. But that was short lived and it hasn't happened since. Whilst it was running, it ran very badly.
If I disconnect the high pressure pipe from the fuel rail and crank the engine, I just get a very slight trickle out. I would have thought it should be jetting out like the aforementioned pressure washer!
So, I replace the high pressure pump. And nothing changes.
The only things I can think of are -
a) The replacement high pressure pump is also defective
b) Whilst it appears to work with the hose disconnected, the low pressure pump isn't coping when connected to the high pressure pump
c) The exhaust camshaft isn't actually driving the high pressure pump. For that to be true, the exhaust camshaft would have had to snap cleanly - unless there is some failsafe mechanism there to prevent cambelt damage if the high pressure pump seizes.
Tomorrow morning, I can easily rule out c).
Anyone have any other thoughts?
My son's 156 JTS cut out completely earlier in the week and the symptoms are very similar except it won't even start.
No ECU faults.
Crank sensor is good ( checked by resistance, oscilloscope and FiatECUScan when cranking on the starter )
Engine is mechanically fine ( checked the cam timing with cam locks just to be sure and did a compression test )
Fuel pressure regulator operates when hooking it to +12v
Fuel gushes out of the hose when disconnected from the high pressure pump ( so low pressure pump is probably good )
Fuel pressure sensor reports 5.5 bar when cranking the engine in FES ( about right for the low pressure pump )
It is unlikely to be the ignition side or injectors - all would have had to fail at exactly the same time. There is no evidence of any cylinder firing.
I did get the engine started very briefly yesterday when I disconnected the fuel pressure regulator. But that was short lived and it hasn't happened since. Whilst it was running, it ran very badly.
If I disconnect the high pressure pipe from the fuel rail and crank the engine, I just get a very slight trickle out. I would have thought it should be jetting out like the aforementioned pressure washer!
So, I replace the high pressure pump. And nothing changes.
The only things I can think of are -
a) The replacement high pressure pump is also defective
b) Whilst it appears to work with the hose disconnected, the low pressure pump isn't coping when connected to the high pressure pump
c) The exhaust camshaft isn't actually driving the high pressure pump. For that to be true, the exhaust camshaft would have had to snap cleanly - unless there is some failsafe mechanism there to prevent cambelt damage if the high pressure pump seizes.
Tomorrow morning, I can easily rule out c).
Anyone have any other thoughts?
I checked the +12v to the pump ( OK ) and the continuity through the pump to earth ( OK - which also checks the inertia switch ) and the relay was bench tested ( OK ).
I then put the key on 'MAR' and disconnected the fuel pipe in the engine bay where it joins the high pressure pump and there is a good flow of fuel through the hose. I'm not ruling the low pressure pump or filter out* as they be ok on 'MAR' but fail to supply sufficient fuel with the engine running. But the amount of fuel being delivered with the hose detached should allow for some coughing/spluttering on the starter at the very least.
So, this morning I'm going to try and test the high pressure pump(s) by driving them with an electric drill after making a suitable adaptor tool. As sparks and petrol often don't end well outside a combustion chamber I shall have to take precautions they don't meet!
If I don't get anything more than the current trickle out of the high pressure pipe I shall have to suspect both high pressure pumps are faulty.
* I don't have a fuel pressure gauge so I cannot be 100% certain the low pressure pump in the tank is OK - but I may have to buy one.
I've ruled out the cause as being c) ( broken drive to the high pressure pump ) which was unlikely anyway. I took the cam cover off, marked the camshaft at the coupling* with a marker pen and all seems well.
No other progress though.
However, the fact that FES reports 5.5 bar of fuel pressure is a lie. I removed the fuel pump relay, disconnected the return feed hose from the fuel rail and removed the pressure limiting valve from the fuel rail so there could not be any fuel pressure in the rail and the pressure sensor still read 5.5 bar. Obviously the ECUs idea of 'zero'.
Likely candidates are still the low and/or high pressure pumps.
sigh.
* the high pressure fuel pump drive peg screws into the camshaft and is tightened to around 100Nm.
No other progress though.
However, the fact that FES reports 5.5 bar of fuel pressure is a lie. I removed the fuel pump relay, disconnected the return feed hose from the fuel rail and removed the pressure limiting valve from the fuel rail so there could not be any fuel pressure in the rail and the pressure sensor still read 5.5 bar. Obviously the ECUs idea of 'zero'.
Likely candidates are still the low and/or high pressure pumps.
sigh.
* the high pressure fuel pump drive peg screws into the camshaft and is tightened to around 100Nm.
Hi David,
A timely and prescient post. I was just about to update this.
Not having a fuel pressure gauge, I decided to make one just so I could be certain about the low pressure in tank pump. I can't wait to get a gauge off eBay.
So I got an old compression tester and sliced off the brass spark plug end. I then stuck a brass bar in the lathe and made an adaptor to go from the compression tester and plug directly in to the quick release terminal that connects the low pressure line to the high pressure pump on the 156. Quite a neat bit of machining for a rush job! I'll post a picture later.
Anyway, I plugged it into the 156 and got nothing. No pressure at all. So, to check my home made tool, I went to plug it into my GTV.
I really should have started the car and let it run out of fuel before unplugging the petrol hose from the fuel rail. One of life's little lessons. Yes, I experienced what petrol at 5 bar is like! And it's nothing compared to what I got from the 156.
Anyway, I plugged in the tool and turned the key. Pressure gauge showed 5 bar. I now know my home made tool is good and although the 156 is delivering the fuel to the engine bay, there's no pressure behind it. Absolutely nothing.
There's still a chance it could be a blocked filter ( I need to check the car has one ) but it is most likely the in tank pump.
Thanks.
A timely and prescient post. I was just about to update this.
Not having a fuel pressure gauge, I decided to make one just so I could be certain about the low pressure in tank pump. I can't wait to get a gauge off eBay.
So I got an old compression tester and sliced off the brass spark plug end. I then stuck a brass bar in the lathe and made an adaptor to go from the compression tester and plug directly in to the quick release terminal that connects the low pressure line to the high pressure pump on the 156. Quite a neat bit of machining for a rush job! I'll post a picture later.
Anyway, I plugged it into the 156 and got nothing. No pressure at all. So, to check my home made tool, I went to plug it into my GTV.
I really should have started the car and let it run out of fuel before unplugging the petrol hose from the fuel rail. One of life's little lessons. Yes, I experienced what petrol at 5 bar is like! And it's nothing compared to what I got from the 156.
Anyway, I plugged in the tool and turned the key. Pressure gauge showed 5 bar. I now know my home made tool is good and although the 156 is delivering the fuel to the engine bay, there's no pressure behind it. Absolutely nothing.
There's still a chance it could be a blocked filter ( I need to check the car has one ) but it is most likely the in tank pump.
Thanks.
Just an update.
I found a brand new Bosch in-tank fuel pump online for an extremely good price ( not much more than some used pumps ).
The car is now running normally.
I wish I'd made that fuel pressure gauge earlier - it would have saved a lot of hassle and head scratching!
Thanks for getting those pump codes off your cars Pud. Sorry I didn't go ahead but the new pump was just too good a deal.
So my tip to anyone with a non starting JTS : Just because the electric in-tank pump is delivering fuel to the engine bay it does NOT mean it's working and delivering the fuel with sufficient pressure. Get a gauge on it and check.
I found a brand new Bosch in-tank fuel pump online for an extremely good price ( not much more than some used pumps ).
The car is now running normally.
I wish I'd made that fuel pressure gauge earlier - it would have saved a lot of hassle and head scratching!
Thanks for getting those pump codes off your cars Pud. Sorry I didn't go ahead but the new pump was just too good a deal.
So my tip to anyone with a non starting JTS : Just because the electric in-tank pump is delivering fuel to the engine bay it does NOT mean it's working and delivering the fuel with sufficient pressure. Get a gauge on it and check.
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