Lpg ecu.

Umitbat · Jun 25, 2021

Hi
The photo is a car lpg fuel system ecu. The problem was misfire and engine dying instead of idling when I took my foot off the gas while driving.
We did a resolder and cleaning of the card and it was perfect for 3 days but misfire started again. But idle was OK. I realised that relays were not soldered I don't know if oroginally no solder or tech guy did not solder back.
And I realised the condensor desire relays were blown too.
I changed the relays and condensor but misfire on low rpmcontinues. And now it is like gas is not enough when accelerating or uphill.

My question is what do relays do in the ecu?
And affect of faulty condensor.
Thanks

narkeleptk · Jun 25, 2021

They switch power to something. Use a pinout and dmm to determine what.

Umitbat · Jun 25, 2021

Ok so do they work like a switch or control injector motion?

narkeleptk · Jun 25, 2021

I don't know anything about LPG systems so I couldn't say what its used for. I would not think a mechanical relay would be for any injector control unless the ecu supplies both power and control or the injectors open and stay open for the duration of the key on.

Do you have a connector pinout or any engine control schematics?

Umitbat · Jun 25, 2021

No sadly not.

Umitbat · Jun 25, 2021

How can I check relays are good?

narkeleptk · Jun 25, 2021

Switch 12 on & off at the coil while using test light to probe NO & NC

Umitbat · Jun 25, 2021

Thanks
I found out that mosfets can cause my problem.
I must check them too. Will look up

KeepItSimpleStupid · Jun 25, 2021

Before you anything else, disconnect the MAF sensor and see if the general health improves. A failure doesn't always set codes. All of your symptoms fit. A disconnected MAF will likely result in less than optimal engine running, but it will definitely set limp mode.

Other issues that are more likely to cause those symptoms, again with no code set:
#1. Spark plug Coils - this could set a misfire code
#2. Wires
#3 Wire routing
#4 Plugs

An bad MAF sensor is an independent problem. You can get anything from unable to keep the car running, extremely rough idle or even unable to start normally without foot on the gas.

Bad wire routing can sequentially 1) Kill the wires, 2) kill the coil and 3) Kill the plug

The MAF sensor is the hot wire sensor in the air stream to the engine. For some dumb reason, they like to us etamper-proof torx screws on it. Just pull the cable with the engine off and try to start the car.

Umitbat · Jun 25, 2021

It runs smooth on petrol problems start when lpg kicks in.
Is maf affecting also running on petrol?? KeepItSimpleStupid

KeepItSimpleStupid · Jun 25, 2021

There is no harm in trying to unplug the MAF sensor.

In that case, the little I know, I might concentrate on the fuel delivery system. That should be the major difference.

Does it have an OBD port? Do, you have a scanner that can read actual numbers from the engine sensors?

Umitbat · Jun 25, 2021

KeepItSimpleStupid said:
There is no harm in trying to unplug the MAF sensor.

In that case, the little I know, I might concentrate on the fuel delivery system. That should be the major difference.

Does it have an OBD port? Do, you have a scanner that can read actual numbers from the engine sensors?

İ will try today
Car has odb but lpg ecu does not.
I will run diag too

Umitbat · Jun 26, 2021

KeepItSimpleStupid said:
There is no harm in trying to unplug the MAF sensor.

In that case, the little I know, I might concentrate on the fuel delivery system. That should be the major difference.

Does it have an OBD port? Do, you have a scanner that can read actual numbers from the engine sensors?

İ pulled this off and idle was high and ran smoothly.
After I plugged back idle was normal and also ran smoothly.
Only problem is hesitation at low rpms and when idling when I press gas it chokes and then rpm rises.

Umitbat · Jun 26, 2021

What confused me is that we tried with another ecu first place and rough idle was gone with it. But I did not test drive the other ecu. And lpg technician controlled everything and found no other problem. And it was also injecting gasoline with lpg. That problem is gone already with ecu refurbish.

rjenkinsgb · Jun 26, 2021

I'd guess the relays control whatever external solenoid valves do the fuel selection, enabling petrol or LPG & possibly different flow limits for LPG.

Umitbat · Jun 26, 2021

It is smoother now but does not Rev normally on power or uphill. Acceleration on full throttle is very weak.

Musicmanager · Jun 26, 2021

After refurbishing the ECU it is not unrealistic to consider it may require recalibration/remap;

Umitbat said:
does not Rev normally on power or uphill. Acceleration on full throttle is very weak.

That sounds like an Injector problem, or possibly a leak on the vacuum line;

Your LPG technician sounds marvellous !

MM

KeepItSimpleStupid · Jun 26, 2021

Umitbat said:
İ pulled this off and idle was high and ran smoothly.
After I plugged back idle was normal and also ran smoothly.
Only problem is hesitation at low rpms and when idling when I press gas it chokes and then rpm rises.

A couple of things are going on here. Unplugging turns on the check engine light, BUT you have to do a "driving cycle" to optimize tuning parameters.

Usually one of the components of a driving cycle is like 50 mph for 5-10 minutes after the car is warmed up.

With the sensor disconnected, it gets no input from cumbustion sensors.

Replace the sensor. Make sure the air cleaner is OK as well.
There is MAP sensor cleaner. It's not always effective.

Umitbat · Jun 26, 2021

KeepItSimpleStupid said:
A couple of things are going on here. Unplugging turns on the check engine light, BUT you have to do a "driving cycle" to optimize tuning parameters.

Usually one of the components of a driving cycle is like 50 mph for 5-10 minutes after the car is warmed up.

With the sensor disconnected, it gets no input from cumbustion sensors.

Replace the sensor. Make sure the air cleaner is OK as well.
There is MAP sensor cleaner. It's not always effective.

Interestingly engine light did not turn on.
Unplugging definitely worked but I did not drive by 50 mph only city ride.
Idle is definitely smooth no vibration.
Only problem is it chokes a lot when I open throttle a bit more at very low rpm. IF I open throttle slowly it revs fine.

KeepItSimpleStupid · Jun 26, 2021

Umitbat said:
Interestingly engine light did not turn on.

Generally you have to reach operating temperature to start running closed loop. The driving cycle tunes the closed-loop response. Codes generally don't set immediately, so glitches get ignored. The check engine light can go out by itself, but the codes are still in history.

Lpg ecu.

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