Fuel pump not priming - car slow to start - why?

eddyvr4

Leaving Skid Marks
Location
SA
First Name
Eddy
Drive
2001 Legnum Type S, 2007 Kawasaki ZX14
I have found swapping back and forth between my old stock pump and the walbro makes a difference to how it starts, good on the stock pump, and slow on the walbro. (just after the cars been sitting for an hour or so) i think that my oring on the walbro doesnt seal so well (i have a couple stuffed in there) , and also maybe the walbro is loosing some prime internally (it is 5yrs old now.) when the walbro was new for the first few yrs it started fine, maybe not instantly like some cars but always on the first turn of the key

ive got a new oring on order that should fit tight, if that doesnt sort it out i might replace the pump. (because also the car is knocking more than it used to, ..seperate thread) im pretty convinced the slow start issue is due to the oring, or the pump itself, considering also the replies above..
 

Kaldek

2 AYC Bars
Premium Member
Location
Melbourne
First Name
Ed
Drive
2000 Legnum VR4 Manual, Ford Territory family runabout, BMW K1300R.
Just cranked mine today and videoed it whilst capturing EvoScan data. The car was still holding 40psi of rail pressure after 2 days.

Started up fine with no stumble, mind you it's 34 degrees here. Will repeat the test when it's colder.
 

TME_Steve

3 AYC Bars
Lifetime Member
Location
NSW
First Name
Steve
Drive
2010 nt did pajero tow car / 2000 6spd gc8 wrx tarmac rally car / 2000 Manual Subaru Outback 2.5 just a car

Kaldek

2 AYC Bars
Premium Member
Location
Melbourne
First Name
Ed
Drive
2000 Legnum VR4 Manual, Ford Territory family runabout, BMW K1300R.
Been hot here last two days - car is starting fine with no initial stumble.
 

Kaldek

2 AYC Bars
Premium Member
Location
Melbourne
First Name
Ed
Drive
2000 Legnum VR4 Manual, Ford Territory family runabout, BMW K1300R.
Seems I haven't visited this thread in a while. Stumble on cold start still, tried to capture some EvoScan data but my bloody cable stopped working and I discovered it needed to be re-soldered internally (on the USB wires).

Tried to get my son to start the car though while videoing it, and he didn't crank the car long enough for it to catch. Second attempt, the car started with no stumble. What the?
 

Kaldek

2 AYC Bars
Premium Member
Location
Melbourne
First Name
Ed
Drive
2000 Legnum VR4 Manual, Ford Territory family runabout, BMW K1300R.
Hmmm another random fact - tweaking the throttle when it was stumbling didn't help either.

But still...why only the first start...why not the next one a few seconds later?
 

eddyvr4

Leaving Skid Marks
Location
SA
First Name
Eddy
Drive
2001 Legnum Type S, 2007 Kawasaki ZX14
because the fuel pump had mostly bought up the fuel rail pressure on the first cranking, so it started quickly on the second try?

ive noticed swapping fuel pumps from OEM to Walbro changes how mine starts (better on the OEM pump) i thought it was the oring and i recently replaced it with a nice thick one, little if any difference. i think maybe the walbro pump itself isnt holding the fuel pressure very well when standing anymore, but i need to put in a new pump to test that theory.... and ive been living with the problem in the meantime..
 

Kaldek

2 AYC Bars
Premium Member
Location
Melbourne
First Name
Ed
Drive
2000 Legnum VR4 Manual, Ford Territory family runabout, BMW K1300R.
because the fuel pump had mostly bought up the fuel rail pressure on the first cranking, so it started quickly on the second try?

Nah, if you turn the key with the clutch out it will activate the pump and prime the rail but not turn the motor over. I can do that for 10 seconds and see the pressure on my gauge but it will still stumble.
 

naughtika

OzVR4 Stalker
Location
Brisbane, QLD
First Name
Christian
Drive
'96 Galant VR4, '17 MB A180, '25 Macan GTS
mine usually does this.. what I do is crank it for a second, let the starter stop spinning.. then start it again.

mine's PFL and does not have the clutch switch.

also, I do not know the pressure in my fuel rail prior to cranking it..
 

Kaldek

2 AYC Bars
Premium Member
Location
Melbourne
First Name
Ed
Drive
2000 Legnum VR4 Manual, Ford Territory family runabout, BMW K1300R.
mine usually does this.. what I do is crank it for a second, let the starter stop spinning.. then start it again.

Ahhh, now that is exactly what I was going to try next. I suspect there is a component of the cold start system which does not "kick in" until the engine cranks.

This will be my next series of tests. A quick tap of the starter, wait 5 seconds, and attempt a complete start. This won't do anything other than narrow down the possibilities, but I'm OK with that.
 

Kaldek

2 AYC Bars
Premium Member
Location
Melbourne
First Name
Ed
Drive
2000 Legnum VR4 Manual, Ford Territory family runabout, BMW K1300R.
OK I cranked the car for half a second this morning and let it sit for 5 seconds, then started it proper. Still stumbled.

I did another fuel pressure test the other day using a video camera on the pressure gauge while I cranked it and it was inconclusive because the bloody car didn't stumble that time. God damn it I need some hard freaking evidence on each test!
 

NuffNuff

1 AYC Bar
Lifetime Member
Location
Victoria
First Name
Damian
Drive
GTI, GTI, FL Manual Legnum VR4
my car starts worse first start of the day with the new engine mounts, it stumbles over itself like it isnt fueling correctly and splutters to a stop after a few seconds. start again and it goes no problem, starts everytime perfectly for the rest of the day
 

Kaldek

2 AYC Bars
Premium Member
Location
Melbourne
First Name
Ed
Drive
2000 Legnum VR4 Manual, Ford Territory family runabout, BMW K1300R.
my car starts worse first start of the day with the new engine mounts, it stumbles over itself like it isnt fueling correctly and splutters to a stop after a few seconds. start again and it goes no problem, starts everytime perfectly for the rest of the day
That just makes me MORE determined to work out what the heck is going on. I need to set up a questionnaire so we can see what mods people have in place.
 

Kaldek

2 AYC Bars
Premium Member
Location
Melbourne
First Name
Ed
Drive
2000 Legnum VR4 Manual, Ford Territory family runabout, BMW K1300R.
'nother cold start test this evening. Car been sitting since 9am, but it's hot here - about 25 degrees out and probably 30 in the garage due to hot engines from the other car and motorbike.

Lo and behold - no stumble. Also the idle is not high like it often is when the car is cold. I'm seeing target rpm in EvoScan of 1,350 with an actual rpm of 1,850 on cold mornings. Got the data here somewhere if anyone is interested.
 

Kaldek

2 AYC Bars
Premium Member
Location
Melbourne
First Name
Ed
Drive
2000 Legnum VR4 Manual, Ford Territory family runabout, BMW K1300R.
Interesting stats from the survey. Seems that most of us (70%) have the cold start stumble. That's only from 17 responses though, so it's not a *huge* sample set.
 
Top Bottom