Does Underfuelling Make Stink Too?

[KRISKARRERA 2 1 Cars]

Just a quick question....

 

If an engine is slow to start up you have three possibilities (according to Haynes): 1. no spark/weak spark, 2. too much fuel, or 3. not enough fuel.

 

Now let's say that there was not enough fuel. When it finally runs is it likely you'd smell fuel? Or is the only way you'd smell fuel is if it was overfuelling?

 

Just reanalysing the old luke warm start problem again on the Mi.

 

Searched on google and found that sometimes the non-return valve in the fuel pump can fail, meaning that as the fuel drains back into the tank you get a vapour lock that really slows up starting. However if that was the case they'd be no fuel stinkage.

[pug_ham 244 3 Cars]

Bad starting can be due to low compression or a couple of valves that aren't sealing.

 

Graham.

[Baz 421]

That would make sense, the fuel smell is probably the fact that it keeps the fuel rail pressured up everytime you crank, then when you do get it started, smelling a bit fuelly/rich maybe.

[KRISKARRERA 2 1 Cars]

True though it starts fine when cold or if it was last run about 5 minutes ago. At any other time takes much longer.

[lee-bg 0]

My 1,8 8v engine has exactly the same symptoms but i havent found a cure yet.

I suspect injectors, but wasnt able to find replacement to test them.

When you kick the accelerator pedal while you 'start/crank' the car does it fire immediately ?

[KRISKARRERA 2 1 Cars]

Nah makes no difference.

[Richie-Van-GTi 72 2 Cars]

compare how fast your car cranks over with a friends if possible, a slow starter can give the issues you describe. The fuel smell on start up is just whats collected during cranking normally. Other than that do a compression test.

[KRISKARRERA 2 1 Cars]

Look at no.2 here please: (just like how mine is: ) http://www.924.org/techsection/3fuel.htm#2...start%20problem

[jtek 0]

924's are mechanical injection, so I'm not sure what the relation would be in the hot start issues to help sorting your problem, but you may be running a tad lean, meaning when you start from warm with ecu temp sensor registering warm the fuelling may not be enough to get the engine into life. Having said that my 1.6 was running lean (17:1 IIRC) for a long time, and it never had any warm start issues. Maybe get it on a gas analyser, if its lean then check all the pipework etc. and maybe tweak the AFM?

 

Fix: sorry just realised you may talking about an MI16? in which case scrap what i said about tweakings AFM's if it has a lambda sensor.

Edited June 25, 2008 by jtek

[Mikey S 29 1 Cars]

have you checked the fuel pressure regulator isnt bleeding the pressure away?.

 

try clamping the fuel return hose momentarily when cranking. if its a pressure problem, that should send the fuel pressure right up immediatley. it should then start almost instantly.