Alfa Romeo Forum banner
61 - 80 of 108 Posts

·
Registered
Joined
·
163 Posts
Discussion Starter · #61 · (Edited)
Just to clarify:
Compression testing was done cold
Fuel pressure in the charts have always been cold and pre-crank values can be seen in the charts
Injectors have never been out, tested or cleaned
The fuel is not “old”. The tank was last filled two weeks ago from a station that sells a lot of fuel.
I can measure primary voltage at the coils and report back, maybe also look at the trigger signal
 

·
Registered
Joined
·
163 Posts
Discussion Starter · #62 · (Edited)
Installed new air filter and MAF (Bosch 0280218401)(did TPS and ECU reset for good luck) - did not improve first start but was good to replace these items anyway. Throttle body was clean and in closed position (was showing ~2% during idle).

I will throw in the new spark plugs as well even though the old ones look OK.

After installing the MAF yesterday, at about 3pm, the car started first time after about 4 cranks, it had not been run for a couple of days. Car drives well.

This morning, no start first go. Took car for a run and using a different scantool (InCarDoc for iOS): MAF idle 25kg/hr, >6500 rpm 330kg/hr (converted from g/s data). These numbers look strange! OBD air temp was 39 in garage while idling. I checked the voltages and ground at the plug: 2.8v (temp), 13.6v (temp supply), GND zero ohms, 5v (maf supply), 1.6-2v (maf signal idle up to @3000rpm). Double checked air leaks.

MES 4.8 gave me no MAF signal, just a fixed value of 5 or 9 (from two runs) - not sure what is going on here! It also booted up missing the errors tab. Might try using FES 3.5 next time

Today: STFTs are 0.0 at idle; LTFT were -3 for both banks after the drive

Accusparks are in and working, will do the startup checks tomorrow morning.
 

·
Registered
Joined
·
4,808 Posts
It mostly looks OK.
Manufacturer diagnostic data if different from EOBD/OBD2 system.
MES displays the MAF data the ECM is using to run the engine.
EOBD is raw data from the sensor (airflow).
That accounts for disparity unless conditions were quite different (AC compressor active).
 

·
Registered
Joined
·
163 Posts
Discussion Starter · #65 ·
Why does MES only show “MAF (throttle closed)” and not actual live airflow data like my other interfaces?

Today’s cold start:
MAR: Pfuel stable at 5.5 bar
Started first go and the Spark plug indicators were flashing at all times during the cranking
Idle: Pfuel 51 bar but drops to zero and back in sync with the MAF result
Rectangle Font Wood Parallel Pattern


Not sure if the starting first time will be reproducible, have to check tomorrow (such a slow process!)
Maybe it was the plugs
If it starts OK tomorrow, I will put the old plugs back in and try again - need to know what the issue is.
 

·
Registered
Joined
·
4,808 Posts
Well the good news is the management system seems to function completely correctly. Hopefully it will be the state of the plugs but the JTS can suffer from poor injector spray pattern and then inlet tract carbon could play a part. I delayed suggesting that because it is really a last try option due to time and expense involved in sorting it.
 

·
Registered
Joined
·
977 Posts
Why does MES only show “MAF (throttle closed)” and not actual live airflow data like my other interfaces?
In mes you can select ‘Air quantity’ and/or ‘Mass air flow (throttle closed’ ie: flow when throttle is closed, only.

I’m not sure if it is relevant but have you seen the ELM 327 interface warning here: Multiecuscan - Diagnostics software for Italian cars

but the JTS can suffer from poor injector spray pattern and then inlet tract carbon could play a part.
There doesn’t seem to be much else left but it’s still strange that it will only start on the second attempt in the morning. Would it be worth monitoring the inlet mode (short/long) the injection time, spark advance and throttle position during each attempt to see if they change? If choking/fouled injectors prevent starting on the first attempt the ecu might be changing strategy for the second? (I’m assuming that for the rest of the day the air and engine are warm enough to start first time, hence it started first time at 3pm after the maf change. When did you start it after doing the plugs?)
 

·
Registered
Joined
·
163 Posts
Discussion Starter · #68 · (Edited)
Thanks for the advice on using MES.
Re the “ELM327 warning”: I just double checked within MES, my interface is KL Vagcom not ELM327!

I installed the new iridium plugs in the afternoon (when I was installing and testing the new spark indicators) before yesterday morning when it started first time.

I will do a little more testing this morning (21 C) like you suggested.
 

·
Registered
Joined
·
163 Posts
Discussion Starter · #69 · (Edited)
Unfortunately, the car had trouble starting again this morning. It started first go but not convincingly.

On the second go, there was weird behaviour - I had to stop the engine as it was idling like it was running on a couple of cylinders. No warning light but code P0606 logged and cleared OK.

Started OK third time

This afternoon: I noticed that one of the spark test plugs was not as tight as the others when I was removing them, maybe it had a poor connection (perhaps caused the DTC). Started first go but a little rough for the first 30s of idle. Went for a run - smooth as Bro 😎 and was idling sweetly back the garage.

Try it again in the morning monitoring the injector time
 

·
Registered
Joined
·
1,036 Posts
Buy the Supercrap equivalent ether spray; cheaper but same strength.

Ideally try to introduce the spray past the throttle plate, a vacuum port is often suitable. It‘s mostly captive on that side of the throttle, so if you do the recommended few seconds, then let it stand briefly - optimum distribution is achieved.
 

·
Registered
Joined
·
163 Posts
Discussion Starter · #75 · (Edited)
This morning intake air temp was 25 and engine temp was 30 C
Squited a little ether into a vacuum port on the intake manifold and it started very quickly. This is how I remember it starting, very snappy (also started quickly first time yesterday afternoon after a very hot day)
Proceeded to start OK for several more goes.
Temperatures equalised to 30 C fairly quickly.

Where does this leave me? Maybe the cold-start parameters are not being met and the ECU compensates on the second go. Could fuel volatility be an issue as Fruity suggested. Is it mechanical or electrical. I don’t know enough about this aspect of engine management to ask the questions except that a richer mixture should be injected when cold.
 

·
Registered
Joined
·
1,036 Posts
I honestly doubt fuel quality is an issue for you. As per @Fruity, I think fuel delivery is somehow the crux of your woes.

Thinking of it like a diesel, my first thought is weak lift pump or its check valve not working. This would result in at least the mechanical pump having to cycle longer to build up a pressure that permits spark (assuming it doesn’t fire the coils if rail pressure is below threshold). A strong HP pump could also draw air through slightly tired O-rings on the “suction” side.

Mechanically logging the low pressure supply with a gauge teed in, over several hours would show if lift pressure was bleeding off. The “short and snappy” alternative would be to jump power the lift pump for 15 seconds before keying on.

Digressing to diagnostics, I have an OBDLink SX cable from Mike at Gendan. It seems to work fine with the licenced version of MES. As a bonus it also plays nicely with the eastern bloc diagnostic software for Fords.
 

·
Registered
Joined
·
163 Posts
Discussion Starter · #77 · (Edited)
Thanks Addo

Re: jumping the lift pump: Can please have a look at the chart of pressure in post #65 (and #56). Chart is a little difficult to read but lift pressure is stable around 5 bar before cranking. Why does the fuel high pressure value jump up and down between zero and 50 bar during cranking? Shouldn’t it be creating a constant rail pressure to the injectors during cranking otherwise how can they deliver the correct spray pattern? Pressure is stable at about 50 bar once the engine is running

I have a fuel pressure gauge. Those LP fuel lines in the engine bay look like they are double skinned and very hard to remove. Any suggestions?

Is the pressure modulation valve on the fuel rail a suspect? The electrical connector was not locked off, might have been a little loose (not 100% sure). Sprayed it and reattached it securely. I read that this is purely an on/off valve so does it need checking?

I am hoping it is not faulty injectors as they are not cheap and surely they could not all go bad at once.

How long should the low pressure system maintain pressure once the car has stopped? I am guessing fuel is is not a circulating back to the tank continuously?

The fuel filter was replaced Feb 2021
Replaced the in-tank fuel pump assembly 2017-18

This post is interesting and raised doubts about MES low side fuel pressure values:

Disconnected connector at elbow of low pressure line and plenty of fuel came out, not sure if it was under pressure or just what was in the line. Even using spreader pliers, I cannot detach the hoses from any coupling feeding the high pressure pump. I could cut the line out between the metal pipe from the tank and the elbow, and replace it with a standard fuel hose (not going to look as pretty). Looks like the fittings might not be universal (??), maybe I can make up a test piece for the gauge that still retains the existing pipes, or get a quick fit tee coupling. I suspect that the orginal pipes may be hard pastic and difficult or impossible to fit a barb into? Any ideas?
Motor vehicle Automotive tire Automotive design Bumper Automotive exterior
 

·
Registered
Joined
·
1,036 Posts
The lift pump only has one outlet, it’s internally regulated and fitted with a check valve to hold pressure over many hours. At least overnight, as a vernacular guideline.

Teeing in first at the tank end is probably simplest if you can bear the residual smell of fuel. You can butcher a dead fuel line for the female coupling and peel off the plastic to expose its barbs for use with regular SAE J30 R9 rubber hose. The male spigot is a rarer beast, not sure where my cut pieces came from but worst case try someone like EFI Hardware for a brass one.

If you get good pressure at the tank and it stands over time, close up there; move to between filter cartridge and HP pump. There will be a quick disconnect at the pump. Be really fussy about cleanliness, like a diesel.
 

·
Registered
Joined
·
163 Posts
Discussion Starter · #79 ·
I manned up and separated the hose from the metal pipe at the firewall.
I have had my gauge for many years, may have only ever used it once. While it was on zero before I pressurised the system, it now sits at somewhere between 4 and 6 when open to air (are these gauges OK if fuel enters them?).

MAR: pressure rose from 6 psi (maybe zero) to maybe 13 (extrapolated). 7 psi is less than 1/2 bar !!!
Disconnected: pressure dropped back to 5-6 psi
Start: started easily first go (35 C) and fuel pressure did not drop from 13 psi, even at medium revs.
I will report the pressure in the morning.

While adding all the fittings I had the quick connect elbow separated so I could flush. With key on MAR, there was high fuel flow but only for 3-4s and then it shut off. I expect this is normal?

Car Wheel Hood Vehicle Tire

Speedometer Vehicle Car Gauge Motor vehicle
 

·
Registered
Joined
·
1,036 Posts
Normally the in-tank pump runs for only a few seconds prior to cranking, and won’t resume until it receives a discernible timing pulse. That’s why temporarily jumping it with 12V just before keying on, can build up a head of pressure to show if check valve is at fault. While you shouldn’t “dead head” it for a long time, a minute or so to get a stable gauge reading is not a problem. If pressure doesn’t approach stable and spec when wiring is jumped, then either pump is weak or regulator faulty.

I had a faulty 18 month old aftermarket pump in a Citroën two years ago, the regulator was extruding itself and line pressure stayed so low it would start with ether but was gutless on the open road due to low supply volume. As the owner is a fellow after my own heart (inclined to thrift) we repaired it by drilling holes and strapping the regulator in place with galvanised tie-wire. It runs well to this day!

Note that once the JTS starts, like a CRD, it will likely have sufficient suction at the injection pump to draw fuel from the tank.

Edit: We have one of these where I sometimes lurk, have added a few more DIY and modded fittings but it’s a good piece of kit. A trick is to tuck the gauge under the wiper arm so you can see it while stress testing.
Brand new ABV fuel injector tester kit | Power Tools | Gumtree Australia Wollongong Area - Wollongong | 1288932768
 
61 - 80 of 108 Posts
Top