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Cranked forever before starting. Fuel system pressure question(s)

EfiniX

Well-known member
Joined
Oct 18, 2012
Messages
647
Location
portland, or
Odd thing, this morning. But first, a bit of backstory. Whenever my car is cold, it typically starts fine. Turns over for a second or two, then fires right up. Only 2 or 3 times have I had to crank it a few times when cold to get it to start. More often, I need to crank it for a while if I start it when it's warmed up, but only if I've let it sit for a short time (maybe 10 minutes or so). If it sits longer, again, it fires right up. And it's not every time, just here and there.

This morning I drove to get coffee and do a little work. Car started cold OK. I let it warm up, as I do, and drove a short distance. Worked for maybe 25 minutes. My girlfriend sent me a message and asked me to bring her back a coffee. She likes this other place close by, so I drove over there. Car was still warm, but started right up. I got to the other coffee shop, grabbed her a coffee, then went back to my car. Crank crank crank and nothing.

Now full disclosure: I've know that my Odyssey 925 battery is on it's way out. 7+ years old and just last weak, I noticed it was at 11.5v while sitting, and dropped to 7.8v while cranking. So I'm sitting there in the parking lot and it's cranking, but it's not cranking in a way that leads me to believe it's got enough juice to start. So I get a jump. With the cables hooked up, it's cranking strong, but still not starting. It took me about 2 minutes to get the engine to catch.

Once it did, everything was fine. The exhaust smelled rich for a few seconds, but by the time the WB was warmed up and showing AFR, I was at 14.4:1. Car drove home like nothing happened. In fact, the car has been running like a dream since the last bit of tuning I did.

My fuel system consists of a Walbro 255 and 950cc FIC injectors. The injectors were cleaned and flow-matched by FIC when I put in the new motor last year, so they only have maybe 15,000mi on them. I've got no surge and no stalling, and when the car is idling, it sits like a rock at 950rpms. It runs great and boosts 22psi without any knock. I mean for all intents and purposes, it's doing great.

The one outlier is this: my fuel pump hanger assembly is bent from the PO and leaks a bit. Evan (EHMotorsports) and i tried to clean it up and get it to sit straight (we also rewired the pump while we were at it), but our efforts proved fruitless. I do have another hanger from Paul (thedsmguy) sitting literally to my left, but I haven't gotten around to cleaning it.

I've read that with the 255 pump, it's not uncommon to have to crank a bit more. I'm wondering if having a leaking hanger might exacerbate this under certain conditions. I'm also wondering if cranking the motor with a nearly-dead battery might have flooded it and caused me to need to crank it forever to get it to go.

One last thing I would add. I know this doesn't mean I'm safe, but I have had the caps and most of the terminals on my ECU replaced.

Thoughts? I mean I might put the new battery in and just go back to the old behavior, but I'm still wondering if that hanger really could be the cause of this, or if this is just par for the course.
 

EfiniX

Well-known member
Joined
Oct 18, 2012
Messages
647
Location
portland, or
New battery and so far, so good....
 

tektic

Well-known member
Joined
Dec 19, 2012
Messages
1,497
Location
ronkonkoma, ny
Does sound mostly like voltage. It cold be cold crank enrichment table value could use some tweeking. Also is your fpr solenoid still attached?
 

toybreaker

iconoclast
Joined
Apr 30, 2006
Messages
3,581
there's some info in this thread about hard starts / fuel pressure





Quoting toybreaker:
Does it do this on a cold start/hot start or all the time?

Do you have a fuel pressure gauge?

Do you have an aftermarket fuel pressure regualtor?

Many of the aftermarket fpr's will bleed the fuel pressure off at shut down, and it will take a momemnt to build again while the engine is operating on the starter.

As a test, just bump the engine over on the starter (and then return the key to the run position) to get the mpi relay to turn on the pump. It'll automatically turn off in three seconds or so.

Bump it again, let the pump time out.

Now, try and start it.

If it's related to fuel pressure loss at shutdown, it will fire right up.

Good luck, and please update your thread with the fix

thanks!




Quoting toybreaker:
A fuel pressure gauge mounted on the fpr would make these next steps a breeze, as it would allow you to see what;s what immediately, but you can make do if you don;t have one installed.

A good next test to narrow down this issue is to clamp off the return line to the tank after the fpr with a radiused fuel line pinching clamp to prevent the fpr from bleeding pressure back to the tank (the fuelline pinchy pliers are available at harbour freight, the cheapy plastic ones work just fine.)

(you can also use a pair of needle nose visegrips. (the naked jaws might damage the fuel line so you can avoid damaging the rubber fuel hose by slipping a short length of rubber hose over the jaws of the visegrips before using them to pinch down on the fuel return hose, not very elegant, but it works /ubbthreads/images/graemlins/wink.gif )

For these tests you will require assistance. (it's good to have friends! /ubbthreads/images/graemlins/smile.gif )



Run the engine to build pressure, then right as you shut it down, have your helper pinch off the return line inbetween the fpr and the firewall.

wait a bit,

then have your helper release the clamp and try and start it immediately.

... don;t bump the starter, just try and start it without primimng the system

If the fpr is at fault, the car will light right up.

If nothing changes, it may be some a faulty fuel pump check valve or faulty injectors that are bleeding pressure off while the engine is shutdown

To verify there is not a problem with the check valve back at the pump (it closes and holds system pressure at shutdown and prevents pressure from bleeding back thru the pump when the pumpis not running), use the clamping pliers/visegrips to pinch down the supply side.

With the engine running, prepare to pinch the supply line

Shut the engine down and pinch the hose off quickly.

Wait for a bit

Prepare to start the engine

While your helper releases releases the clampy, crank the engine up.

If it starts immediately, the check valve in the pump may be faulty

If you have an injector or two leaking down, neither of these tests will change anything.

To eliminate that possibility, pinch both the supply and return lines

wait a bit

then release both and crank it up


If this test doesn;t show any improvement, you might have some injectors leaking down.

Usually, if that's the case, it'll light up kind of lopsided/lumpy like and run rough for a few seconds as the wet cylinders burn off the excess fuel.

One last tip;

Many of the chip guys can put a "prime" feature into their chips so all you have to do is turn the key on and it'll run the pump for ~ five seconds, no starter bump required, and that'll go along way towards minimising the affect of an fpr that leaks down. I *believe DSMLink also offers this feature in their selectable options, so that may be an option as well.

As far as the afr's, Hertz is spot on, we need to know your fuel trims in order to advise of you of a course of action.

Good luck, and please keep us updated on your progress!



edit
... you can also tell her to get her own damn coffee! /ubbthreads/images/graemlins/devil.gif
 
Last edited:
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