HELP - Diffcult Start-up

[svsgt1]

Hey guys got a question for you. My engine has had trouble starting lately (seems to be flooded ro somethihng like that). I recently re-did the entire fuel system and have much stronger pumps now. The fuel regulator, rails, and injectors are all stock. The engine was running very rich before I modified the fuel system. It is still running very rich as a big puff of black smoke will come out when you rev the engine. Anyway, the engine doesn't want to start very easily and when it does it chugs along for 5 seconds before it really runs smoothly. Plus it doesn't idle well and will stall out if it idles too much below 1000rpm.

Could this be because the engine is getting more fuel with the new fuel pumps even though the regulator has not changed? I did replace the timing belt but it was put on properly as the timing marks always lined up with every revolution. The engine also back fired a couple of times during the initial startup. The way I have been able to start the engine is to disconnect the fuel pump and start it and let it run off what fuel is in teh system. Then reconnect it up and it will start like stated above. Is thsi purley a tuning issue or can it be something else?

Thanks,
Adam Grosso

 

[Peewee]

Even with a large fuel pump the fuel pressure regulator will keep the fuel pressure at the correct pressure.

Under no circumstances have I ever seen a factory setup run rich enough to cause black smoke.

Are you sure you are firing on all 8 cylinders?
Is there a chance your spark plugs are on their last legs?
Do you still have untouched factory management?

 

[madmont]

Factory pressure a idle with vacuum is 28-34psi
without vacuum at idle it is 38-44 any more is probably detrimental
the factory regulator was unable to cope with the extra pressure from my vl fuel pump and I added another to bring it into specs

 

[svsgt1]

Well I would assume it is running on all 8 cylinders as when it starts and runs it does run well. It purrs great at 2000rpm and I was reving it up to 4-5k without any issues. The engine management is a LINK ECU that I have not touched since last time it ran so that didn't change. The only thing that did change in the way of the engine running was the fuel system. The new pump is a Walbro 255 l/hour external unit. The only other things I did was replace the cam oil seals which required me to take off the distributors and cam gears. I must have put it back together correctly otherwise the whole thing wouldn't be running at all I would assume.

Here are the problems I am having.
1) Difficulty starting the engine. When cranking it fires up but will stall itself out or will sound like it is running on 4 clynders for about 5 seconds and then kick and and run like normal.

2) Running rich. It did this before the mods but I noticed that there was more black smoke coming out after I added the new fuel pump.

3) Not being able to rev the engien quickly. This happens mostly when the engine has not run for more then 10 min and when you step on the throttle to quick it sounds like it will stall much like it does when it starts, almost exactly. but if you opn the throttle slowly it revs just fine. Or if the revs are already pretty high it will rev quickly without a problem.

Any suggestions on what it could be? Does the LINK ECU need to be retuned? As far as I can tell there are no 02 sensors on the car, they are definietly NOT in the exhaust. But the Link ECU does have a vacuum line going from the manifold to the computer itself. Could it be possible that the throttle position sensor is screwed up?

Thanks,
Adam

 

[Peewee]

Yes, the Link ECU does need to be retuned.

I did this on mine.
I got a Microtech ECU and used the factory fuel pump. Had it tuned with that setup.
I was having issues, thought they may be fuel related, so bought a Walbro.
After that I was getting full fuel pressure, and thus overfuelling compared to the factory fuel pump (18years old).

I was getting black smoke clouds at idle too, and after a week or so it started to become harder to start.

Get it retuned.

 

[Lextreme II]

SVS,

I think you are running too rich and you tried to lean it out and it because too lean and the computer will compensate by rich it out. Try to increase the fuel program slightly and test it out. Secondly, when u program the software, make sure 0 psi and 500 to 1000 rpm has the same cell valves as idle (-18 psi at 500-1000 rpm). If your 0 psi is different then u will have a hard time starting.

Please check the program pattern for 500 rpm and 0 psi, 1000 rpm and 1500 rpm and so on. http://lextreme.com/PDF/R4_sample.pdf

 

[gloverman]

The link ECU are generally easy to work with. What is the motor in? What model Link do you have?. Do you have a Hand controler or laptop connector? Is there any chance a RELOAD has been performed while this work has been done? because this would give the symptoms your car has providing the cam timing is correct. If you have a version 5 link I have access to the initial map they are sent out with. This may be a good place to start at. Cheers

 

[sideshow]

its hard to explain as i got taught this ages ago

by increasing the flow of a fuel pump you do actually make mofre fuelk enter the cylinder even thought the fuel pressure doesnt change

the injectors stay open same amount of time as before but now u have more fuel flowing thru due to more flow from the pump

if the pump was only a gradual increase then u woul dnot notice but if its much more flow then u would

but why dont u look at it this way

u have a link

it is fully programmable

why not just get it retuned

if the enigne was runnin rich slightly
now its just abit more richer

then the original tune was not a good one anyway

its not an electrical or mechanical problem

u have just increased the flow of fuel to the engine so just retune it and its all fixed

 

[cribbj]

its hard to explain as i got taught this ages ago

by increasing the flow of a fuel pump you do actually make mofre fuelk enter the cylinder even thought the fuel pressure doesnt change

the injectors stay open same amount of time as before but now u have more fuel flowing thru due to more flow from the pump

Sorry for the thread drift, but Sideshow, please take a shot at explaining this. I'd like to understand how more fuel can enter the engine if the FPR is working right, the deltaP across the injectors stays the same, and their pulse width doesn't change? What I learned in physics says it can't, but this might be one of those bumblebee situations..... :veryhappy

John

 

[sideshow]

well i got told by a japanese mechanic how worked on alot of hi performance race cars

but if u put a pump with alot more fuel flow then u will have more fuel flowing thru the return line

so then y wouldnt u have more fuel flowing through the injectors

its only a minute amount of increase and i havnt done any tests but i had this mechanic explain it to me i didnt not figure out why it would

but its what he told me so without doin tests i cannot prove it

the only way to see if this is true os of the above person refits his original fuel pump and sees if the running rich problem gets less like it was before

all this could be wrong im not sure so if anyone had any proof lets us know

 

[cribbj]

With due respect to your Japanese mechanic friend, I think the only parameters that determine how much fuel will go into the cylinder are the pressure of the fuel at the injector (relative to the manifold) and the length of time the injector stays open. However, as you say, it would be an interesting test, if all other things could be held constant.

I'm wondering if his pump may have been flowing more than his return line could handle at idle, and this caused the (relative) pressure in his rail to run higher?

John

 

[sideshow]

yer i know i have no proof

and its prob inaccurate assumption without proof


im just tryin to explain it how i got told

but i do know that these days a normal fuel pressure gauge is not always good

its best to use a fuel pressure and flow tester

pity they cost about 700 bucks hehe

but if u have more fuel flow thru the fuel rail and the fuel press reg does have a slight restriction raising the fuel flow with a new pump ould inturn make the mixtures go richer

ill ask afew more people in the industry see what they recon

im goin to try fit a better pump in my hilux

im just wondering if the one i have inside the tank is just not enough

pressure might be ok but flow might be low especially for a v8

this might be why its pinging sometimes

but anyway thats another issue

 

[svsgt1]

Sorry for the late reply but I have been with out power as we just got hit by a hurricane. I live in Ft. Lauderdale FL so we got it pretty bad but no major damage. Anyway, I know I need to get the ECU retuned for sure. I have an older model LINK and I am sending it away back to the manufacturer to get it upgraded so I can program it with a laptop.

Anyway I'm not sure about the fuel pressure and flow ratio that was explained above but I do know that with pnuematics that you get a higher flow rate of air when the pressure is lower. Like with linear actuators the lower the pressure the faster the cylinder will move as the flow rate is higher but it wiull not have muych force. As when teh pressure is higher the force of the linear actuator is greater. Don't know if that helps.

My setup I have 2 pumps. One pump takes fuel from the main tank to the small external surge tank. The second pump takes fuel from the small external surge tank to the engine. The return line from the engine goes back to the small external surge tank. The surge tank also has a return line that goes back to the main tank. The surge tank should always be full but this poses a good question as to whether there is pressure in the return line from the pumps putting in too much fuel into the surge tank. I don't thgink this is the case as this setup is common in race cars and everything is either an AN-8 or AN-6 line so that shopuld be able to handle the flow from these pumps. Anyway I will get my Link ECU upgraded and then get the engine tuned and let you guys know how it goes.

Thanks,
Adam

 

[Madaz]

Hi there, did you ever get this problem sorted?