FAO: Tom; Problems on Re-Start (LPG in HGT)

[Anonymous]

Hi Guys,

The authorised dealer of Teleflex GFI installed the SGI LPG kit to my highly modified 1998 Fiat Bravo 2.0 20v HGT !

The engine runs smoothly & without any problems on LPG except Engine re-starts !

The problem occurs when I stop the engine at LPG mode !

When I run the engine on LPG & shut it down at LPG mode & try to re-ignite again, It simply refuses to start.
(Every engine starting sequence begins with Gasoline mode as you know!)

The battery is OK, the Spark Plugs are new & the engine cranks...
Unfortunately the engine seems NOT starting !!!

I need to pump the accelerator while I'm cranking the engine in order to start it & although I'm pumping the accelerator, it takes ages for my engine to start in Gasoline Mode !

But check this out;
If I try to shut the engine at Gasoline Mode (by simply de-activating the LPG mode from the control button before shutting the engine down) it re-starts Perfectly !

So, as you can see I do have a problem with Engine re-starts which have been previously shut down at LPG mode !

As a summary,

- If I shut it down at LPG mode = It cranks for ages & FAILS to start !
( I need to pump the accelerator several times in order to start it !)

- If I shut it down at Gasoline Mode(by de-activating the LPG mode before shut down.) = It starts PERFECTLY !

- I don't have any problems on engine starts after several hours. It cranks & ignites beautifully It doesn't matter If I shut it down at LPG or Gasoline mode ! (Meaning the morning starts or after a long period of time like 5-6 hrs.)

What can be the problem & what should I have to check in order to have a succesful Engine Re-Starts which have been shut at LPG mode ?

All ideas & help are welcomed. Thanks in advance

 

[tommy k]

on our land rover wen it was gas converted there was a bit of a start up procedure from cold and a different one when warm/ re-start.


From cold, had to be started on petrol... then put the switch to the middle to stop the fuel pump. Drive down the road and wait for it to loose power due to no fuel and then switch over to LPG.



On restart just leave it over on LPG and it will start as normal and carry on driving.



If you wanted to start on pertrol tho you had to let the pump suck the petrol to the engine. Most cars only pump for a short time so as in the case with our landrover you turn the key on... wait for the pump to stop, turn off and back on and let the fuel pump, pump some more



I guess this will be the same on the HGT... when your trying to restart on petrol, the pump hasn't pumped the petrol to the injectors yet hence it will not fire.

If you must start on petrol, let the pump turn on, off, on a few times befor attempting to re-start.



Why must you re-start on petrol tho?? The only reson to start on petrol is because the vapouriser uses the hot water from the engine/ radiator to help turn the LPG from a lquid to a gas....


When the engine is warm you don't have this trouble


Hopefully Tom may add some more details but this should help I hope.



Tommy K

Tommy K - Have you got the Bottle!!

 

[Tom]

Sounds like the LPG ECU is not adding enough petrol for a hot start. The dealer should be able to adjust this.

No helpful info on the teleflex website.

 

[Greg]

Hiya Mate was just wondering around what price it was for the conversion, and dose it lose any power by running it on LPG....

The Mean Green Speed Machine!

 

[Boorock]

Hi Guys,

Thanks for the advices but the dealer is simply lost...

They simply don't know what is going on & thay don't know what to do.

They have some assumptions though: Rich mixture !

When the LPG shutdown engine asked for the re-start the fuel pump maintains the pressure & the fuel injectors began injecting fuel over the LPG filled cylinders.

So the result is a very rich mixture for the ignition sequence which fails unless I pump the gas pedal & let the butterfly valve open so that the cylinders suck the air needed for the start.

While cranking & pumping the gas pedal, as the cylinders began sucking the air mixture reaches the optimum ratio so that it can be ignited.

This is their assumption & they don't know how to solve it !

I've sent my LPG ECU programs to Netherland (Teleflex HQ) May be they can sort the problem out ?

As for the LPG performance; unfortunately I haven't dyno'ed it yet but I can say that there is a very,very slight difference.

As in scientific terms there should be some loss because of the CR (Compression Ratio)& the MON/RON values of LPG.

The optimum CR is 12:1 for the lossless LPG motoring. And also LPG don't have the enough calorific value as gasoline.

As of the CR & the low values of LPG, the general loss stays @ %10 - 15

The LPG is half the price of gasoline & I2m simply happy about the %10 loss of power which will return in terms of economy.

And if I need that gasoline power, I can touch a button & get all of it

 

[donny lad]

HAVE YOU NO MORRALS MAN!!

thats one less decent hgt off the road now, you should have baught a jtd if you wanted echonemy!!!

shame on you!!!!!!!!!!!!!!!

 

[Boorock]

Shame on the Petrol Companies & the countries that add enourmous tax on it !

Not on me

Also I think I made the right choice because there's nothing wrong with some money saving.

As I mentioned before If I do need that %10 power I will just push a button while driving and Voila: Here comes the 174 Bhps back on !

The best of two worlds in the same car

Got the point ?

 

[Tom]

When you pump the pedal it will add more fuel. If it was a case of too rich mixture then holding the throttle open would clear it.

 

[Boorock]

Thanks for the immediate replies Tom.

U're a real specialist & very helpful as always

Some of the technicians insisted on the same thing (Poor Mixture) and told me that some of my gasoline injectors maybe weeping & while driving @ LPG mode it can drain the fuel line making the gasoline pressure decrease.

So that when I try to re-start (after waiting for the speedo lights going off) the fuel pump can't send enough gasoline to the cylinders.
Resulting in Poor Mixture so that it won't ignite.

Also he suggested that my fuel pump can be faulty..?

But here comes my questions about that poor mixture theory.

1- While I am driving @ LPG mode & switch to gasoline from the selector (button) the engine never hesitates. I can't feel the switching between LPG & Gasoline. If there is something wrong with my fuel pump, shouldn't it affect the LPG-Gasoline switching making the engine gag for a second ?

2- If I run the engine at gasoline mode by deactivating the SGI system from the selector (button) for a few seconds prior to shut down & try to re-start; it starts perfectly ?

Now, any ideas about the problem ?

Is it software related or Is it because of my fuel system (Faulty Pump / Weeping Injectors) which is probably faulty ?

PS: They are insisting on that this is the most weird problem they ever met !

 

[Tom]

If it was a fuel pressure problem it would affect ALL starts, hot, cold, petrol or LPG.

The fact its just hot LPG starts indicates its the LPG system.

Is there no way to make it always start on petrol rather than LPG? You've got a fairly well modified engine and the LPG kit will have been designed for a stock engine.

 

[Boorock]

Dear Tom,

Most of the latest SGI systems on the market have gasoline starting until the radiator warms up to 40 degrees in order to convert the liquid LPG to vapour.

When all those systems including Teleflex GFI are active; they start with petrol & automatically switch to LPG.

In my engine I do the switching manually...

Deactivating the LPG System before shutdown manually at any time means the following re-starts will be on standart gasoline mode. Letting the successful re-start at the gasoline mode.

In this case Teleflex GFI won't turn on until I switch to LPG mode manually.

The technicians insist that this weird re-start problem occurs because of my modded engine...

They even offered a full refund If I am not happy with it but I can not decide whether to keep it or try another SGI system

The Teleflex GFI system known as the exclusive kit upon all LPG conversions. It has a seperate MAP sensor, LPG injectors installed on the manifold... Meaning a perfectly un-noticable montage without any visible cables & hoses on my engine. They did hide the LPG ECU & the interface...

The engine still looks exactly the same before the SGI system installed

No one can understand that my engine has a dual fuel; LPG conversion !

I really like the performance of this SGI kit, it never switches to gasoline mode at hard conditions. (Not even @ 7.500rpm! To be precise, we monitored the SGI system by a notebook connected to the LPG ECU while driving )

The consumption is definitely good meaning %40-45 in terms of economy.

So what do you recommend ?

Should I keep it or try another SGI system ?

 

[Boorock]

Forgot to mention;

When the SGI system is active it will always start at gasoline mode whether the engine is HOT or COLD.

The LPG ECU decides to wait for more warm up or switches to LPG mode depending on the temperature of the engine.

 

[Tom]

The hot start issue is due to your engine. Can they make it always start on full petrol no matter the engine temp?

 

[Anonymous]

"The hot start issue is due to your engine. Can they make it always start on full petrol no matter the engine temp?"

The SGI system always start in petrol mode.
The temp doesn't matter. Whether it is HOT or COLD !

It is starting in petrol mode but, if you shut the engine while it is running on LPG which means the Teleflex GFI is active (as U should do...) The following re-start (Which is on petrol mode) fails

But, If U do run the engine at petrol mode simply by deactivating the Teleflex GFI from the selector before shut down for a few seconds the following re-start (Which is on petrol mode but Teleflex GFI is OFF) succeeds

As U previously mentioned the problem points the LPG system.

How do we decide if it is the Poor or Rich mixture ?

Any ideas ?