mark kibort

Hey folks,

I know you all have heard this question before, but the friend with the '88 stroker cant get it started. its run kind of spotty over the years, when i had it , we got it running pretty well, but occasioally it would floodout on start up and dont know why that was, but eventually, it would start, make a bunch of smoke and then run fine. Now, after doing some window wiring work, he cant get it started.

I was suspecting a leaking injector (if that is posible for an injector to leak fuel after the engine was turned off) as a cause for the loaded up starting issues. but , after going through the normal chasing of the tail, process of jump'ing fuel pump relays and things, it still wont start.. he says, both bank fuel injectors are clicking. fuel pump is running, and he says he sees a spark on both disties.
so, i had him disconnect fuel regulator (RRFR) vaccum line and put a vacuum on the nipple... it held vacuum.... but then checked the dampers, sure enough it didnt hold pressure and then gas came out of the vacuum gauage . not a lot, but a little. so, somethings leaking on the Damper... (diaphram?)

before that, had him crack the fuel line nut and gas only poored out, not sprayed out like it was under normal pressure as we have seen before.

can a slight crack in the diaphram on the damper cause enough fuel to pass into the intake. or maybe its allowing all the fuel to be pushed back into the fuel take , like the RRFR does? (i dont know how dampers work and if there is a return line that can hurt pressure being kept in the lines)

im going to see the car tomorrow and thought the wiz kids here might give me something to go on.

thanks,

Mark

Randy V

Of course it is a possibility. The fuel system stays pressurized after shutdown.

Leaking injectors are often the cause of a hot-start problem.

After driving the car and shutting it off, it is difficult to restart after a short period as the injectors are leaking under pressure and loading the cylinders with fuel, causing a flooding condition.

After sitting for a few hours the fuel dissipates and the car starts normally.

FredR

Mark,

f the diaphragm has gone the system will not hold fuel pressure and thus make starting more difficult as it tries to build pressure. I doubt the diaphragm failure would be so severe that fuel pressure cannot build up but...?

The rapid opening and closing of the injectors creates shock waves- the fuel dampers are simply rubber diaphragms that help absorb the pressure pulses by being able to flex. I am not sure why the other side is connected to the inlet tract- quite probably to safely ingest any gasoline if they fail. The fuel pressure regulator is connected to help keep the fuel rail pressure differential [to the inlet tract] constant but the dampers are something else [I suspect].

Regards

Fred

mark kibort

The fuel pressure regulator has the vacuum line only to reduce the pressure under idle...... its a minor adjustment to fuel pressure. drops about 4psi or so. as soon as you floor it, the pressure the spring is set at in the regulator , sets the line pressure. so, how does it fail..... and what is that 3rd line do off the damper? if a damper is bad, can it reduce all the line pressure through that return line?

FredR

I very much doubt that a diaphragm failure [and the resulting side stream flow] will be such that the pressure delivery can collapse to the point where the system will not fire up- I do not think the vacuum line will allow sufficent flow to do that but it may reduce the fuel rail pressure a little.

Either way I would not try to run a motor if a damper has failed as pressure may accumular and then blow off the vacuum line that was not intended to see fuel pressure exposure.

Fred

Speedtoys

Returning to a stock system and tune, then some PEMS and sharktuner, and you'd be in a much better position.


But that's just where the smart $ is at.

mark kibort

Yeah, that 3rd line on the damper is the fuel inlet line... the other damper is just an in and out, so that cant do anything. your right, that vacuum line must be a leak safety function. anyway, the answer is check the fuel pump for pressure (at the inlet line) and then the fuel regulator (change to stock) see if that does it.

Rob Edwards

How big are the injectors?
How old are the injectors?
How old is the MAF?
How many ohms across pins 4 and 6 of the MAF?
Which RRFPR is in it? Kirban? Where is the pressure set?
LH is known good? (both banks of injectors clicking- how much clicking?)
What chips are in the brains?
How is the fuel map different from stock to accommodate an extra liter of displacement and not go dangerously lean at the top? Or is it just the RRFPR?

Mrmerlin

after answering Robs questions
I would suggest that these units should all be replaced.
both of the dampers and the FPR

FWIW any fuel smell in the vacuum lines indicates a leak,
and this will usually flood the engine on startup,
and in a worst case scenario you could hydro lock the engine .

Ducman82

bad FPR or damper leak is like the #1 cause of hot start issues.

mark kibort

the injectors are old, 30lbers from devek. same design that we used on my engine, but i think was very premature. 24lbers would have been sufficient.
ill check the Ohms... 4-6 pin
RRFR is the devek porsche one. same one i have set at about 44psi now. (remember, was way down in the teens to fight knocking issues way back when)
stock brains no mods

probably the reason for the hot start issues back when i was driving it 3-4 times a week. intermittant though, but it was a bitch when it flooded.

for sure, that damper must be leaking..... so that has to go... its the damper where the fuel goes into the system.. the one in front, right?

Rob Edwards

So 30/19ths too rich from the injectors, +/- the difference in the opening times between those injectors and stock, multiplied by (X MAF ohms /382 times * unknown coefficient for MAF aging), multiplied by (44 psi/3.3 bar spec fuel pressure). All dependent on a stock LH map. Got it. Just tweak the RRFPR a bit, that'll re-jigger it.

Speedtoys

The trick to making your 'computer' driven car working right, MIGHT involve "computer ****".

Pretending it has a wicked carburetor on it, isn't moving your forward.

In 20 words or less, what's keeping you from doing it like everyone else?

mark kibort

Rob... uh... we did that with my engine. it produces maybe sligly less hp than would be expected out of an optimally tuned 6.5 liter. rember, i got 335rwhp out of this same set up with 72psi on the regulator and a 5 litre. It was near 90% duration time, but thats fine on the 19s and the fuel air curve looked safe and near optimal for all operation.
you dont seem to remember that i took Bill up on the shark tuner testing, and found that mixtures were in the safe range with no knocks. you have to remember, im more about safe than optimizing. all i need is a perfectly tuned engine that is tuned for one particular day, and then go out in a 30F day and ping my motor to death for being too lean.

currently, I'm at 44psi too and the fuel ratios are very nice. 11 to 12:1 no matter what the temp, at WOT. plugs are clean. tail pipe has a normal carbon coating and this same set up , came off the 5 liter with 72psi where the engine of 20 years, looked like it was brand new. heads looked great too. '

so, i dont know why you get so up in arms about using a fuel regulator to get near the optmal zone for mixture. sure i could further optimize by a new ecu and chip, but then i might be temped to change timing around, use 110 octane and blow the motor for some tuning parameter that YOU dont know about . gosh, that would be the first time that has ever happened!!
what do you think you would gain on a stockish 6.5 liter already making a solid, 375rwhp and has been producing that for over 6 seasons now? 10hp? 20hp?
anderson's were 410rwhp with bigger valves, bigger headers, ported intake and heads, as well as dry-sumped. I think all , but you might agree, my set up is not that far off.

want a list of guys that blew 928 motors trying to improve on stock? not saying it cant be done, but i think my success record stands on its own (and that of Anderson and Fan, who also used bone stock ECU settings and a fuel regulator to control mixtures.

Speedtoys

" i think my success record stands on its own"

Ok...tell us about your success. This car's life under your care, has been interesting, but not successful.

Put the threads together so we can all review your tuning prowess.

Luck is not success.