Originally Posted by mark kibort

we are well beyond that... we went back and forth with the relay. its working fine.. you can hear it engage at start up.

Originally Posted by hb4

Oh. Sorry; I must have missed that. If the fuel pressure's the same with or without the jumper now, then maybe either a back or a forth fixed it somehow. A relay with burnt contacts will still click if the contacts aren't already stuck together, but you must know that and have moved on.

I had an LH that failed after a hard-to-start episode. Louie fixed me right up.

Originally Posted by Hilton

Sounds like bad MAF to me from your description of getting it to start with lots of smoke and running badly. However, you need a process of elimination or testing to confirm that conclusion.

So borrow some parts for your racer.. specifically the MAF and LH brain.

Swap the brains first to see if there's a difference in behaviour. Then put back the original LH and swap the MAF.

In addition to the MAF and LH, other suspects in no-start are:

Fuel Pump relay
LH relay
Temp II
O2 sensor
Fuel pressure (need to fix the leaking fuel system regardless - it'll cause warm start issues due to fuel pressure dropping in 4s - fuel pressure should hold for 30 mins)
Lack of spark (seems you have spark)

Given the coin the owner must've dropped in buying a devek stroker in the first place, spending a thousand bucks on a used FPR, replacement dampener and getting someone to spend a few hours with a sharktuner on a dyno should be a no-brainer. I don't care how well you say it runs at part throttle, tuning with an adjustable FPR is a compromise for the other 75% of the rpm range - its not like this is a racer which spends all its time at a set RPM range.

Lots has changed in the 928 world since devek stroker days, and the owner would have adjusted his expectations downwards for how well a 928 can run to match his ownership experience. The owner might actually enjoy driving the car more if it ran dependably like a 928 should.

Originally Posted by Speedtoys

The continuing saga of your success..

Originally Posted by jcorenman

Hilton's list is terrific, print that out and keep a copy.
I would also recommend re-reading post# 2, 3, 5, 6, 8, 9 10, 12, 13, 15, 17, 18, 23, 24, 29, 31, and 33.
Those are the smart guys here, you really should follow their advice.

We're on the third page, you mentioned leaking dampers on post#1 and they've been mentioned 3 dozen times since.
Just change the freaking things (and the regulator, if that leaks) and then see what you've got.

And yes, hot ECU's are bad. But given that this problem started with the owner in the wiring, my advice would be to test his ECU's in your car rather than the other way around. Bad wiring can fry an ECU, the converse is less likely.

Originally Posted by mark kibort

... fuel doesn't leak out of the vacuum port, it only can be pulled out with high vaccum applied ...

Originally Posted by mark kibort

yes, the fuel pressure is crazy low unless I jump the fuel pump relay.... that doesn't meant the relay is bad, it means something isn't triggering it.

Originally Posted by mark kibort

can a bad MAF do this?.... maybe the maf is showing tons of air flow , while none is present, so terribly rich. what about that hot LH jet box... sounds like it might be blown up.

Originally Posted by mark kibort

don't think the 02 sensor can do anything... ive run mine fine with and without it, no issues.

Originally Posted by mark kibort

Temp II... hmmmm I wiggled and that's when it started up and didn't run realy well.. heck I was right there with the meter and should have measured the resistance.

Originally Posted by mark kibort

LH relay? we didn't check that. maybe just put jumpers on the LH and ezk relay spots to make sure they are getting powered up.

Originally Posted by mark kibort

when it runs, it ran pretty nice.. I don't see any compromises by using the RRRFR. what do you think those gains would be besides a few hp gain? part throttle start up, etc when things are working, was really nice.

Originally Posted by jcorenman

Vacuum is 15 psi, max, across the diaphragm. Fuel pressure is 55 psi. It's a leak.

There are three levels of uncertainty when troubleshooting: The "likely", the "unlikely", and the "impossible".
Leaking dampers aren't any of those, they are "certainty". Fix the freaking things, then start troubleshooting.

Originally Posted by Speedtoys

If you listened to -anyones- advice on -anything-, you'd be in a better place with this.

I'm not the troll.

You keep doing it, well, wrong. You just keep coming back. And it's not for a lack of people asking to help either.

Who else has done what you're doing with similar, success?

Originally Posted by Hilton

I'll deal with the parts about diagnosis first in the hopes they get read before the red-mist descends and you fight the "tuning with an RRFPR" corner...

>>>>>>>>>>No worries.. thanks for the help..... actually, i have had great luck with the RRFR on both the Ljet and the LH. i dont see any downfalls , but we can address those possibilities later.



At this stage, you're fighting more than one issue. Fix the fuel system leak - its not just affecting fuel pressure, its putting unmetered fuel directly into the intake which will affect the mixture too.

Then you can move onto finding out the source of any fuel pressure anomalies.
>>>>>>>>>>again, there is no unmetered fuel when the lines are disconnected



Yes, a failed or out of spec MAF forced a fixed injector pulse and the car will barely start or run (limp home mode), including black smoke at startup and not holding idle. When the LH detects an out of range MAF signal, it defaults to limp home mode just as if the MAF was totally dead.

The simple test here is to unplug the MAF and see if it behaves the same still, as that forces limp-home mode. A more advanced test it to use a known-good MAF, which you conveniently have on your race car. Even more advanced is to send it to Louis Ott to put on a flowbench and test.

>>>>>> great advice... illl see if he can do this test. although, remember, i have no tach signal to the dash.... could that MAF interrupt? sure sounds like that, with all the other issues point to bad LH box. its more than a bad idle, its barely starting and when it does catch it sounds like 4 cylinders running that are themselves flooded.




If you unplug the O2 sensor, the car will run very rich, and the idle will hunt (it runs rich because the LH see's 0V all the time rather than alternating hi/low). If you plug an S4 into a sharktuner all this LH behaviour becomes very obvious. Its a fantastic diagnostic tool.
<>>>>>>>>>>>>>no , this is not true at all. the o2 sensor makes the closed loop operation possible, so its the feedback to the system and there, you have hunting. more so on the Ljet versions. without it, its not that rich, as it goes to a steady state 12.5:1 or so, and it runs fine... sure emmissions are high, but it runs just fine. ive tested this at the dyno as well, WOT , not effected, and idle and part throttle its just the mixture you would get if WOT .... Im sure you can see more on the shark tuner, but in actually this is not a possible factor unless there was a short or something effecting the ecu via the o2 sensor..



Yes - measure resistance on both sides of it (its two sensors remember - one for EZK, one for LH) with the meter set to resistance (ohms). The workshop manual defines the specs for what the sensor should read at various temperatures - if it matches spec at ambient, personally I'd assume it is ok for now until you've verified everything else which affects fuelling, and are onto the "unlikely" round of troubleshooting.
>>>>>>thats the two wired sensor near the oil filler on the S4? so , one side to ground and then the other side to ground? i remember how bad that can effect start up. Scot had one on his 5l 84. it was bad, shorted out when the engine was put in for mis wiring that loom. cooked it... diagonosed by the meter and then confirmed by using a 600ohm resistor and it started up fine. (and ran until the resistance needs to change )

Wiggling and identifying correct cause-and-effect are not compatible. People who do this end up with some voodoo starting technique involving wiggling, unplugging/replugging, and crossing fingers, and when it doesn't "work" they start questioning their own ability to do voodoo, instead of troubleshooting the car's failure modes.
>>>>>>>>>>>agreed



There are 3 relays you need to be concerned about - LH, ignition, and fuel pump. Rather than a shotgun jumper-everything approach, how about just one at a time to see if anything changes about the visible symptoms.

I'd even be tempted to just replace all 3 with new (and tested) type-53 relays because they're cheap and it'll eliminate one of the most common failure modes from consideration not just now, but in the future.

>>>>>>>>>>we did this systematically. no change they all seem to work ok.. the fuel pump relay is special right? isnt why the fuel pump runs for 4 seconds and then quits? is there a timer circuit in there? dont thin they are the issue for the other reasons listed above.

ok.. now onto the "lets have an internet fight" part



The gains from proper tuning instead of using an RRFPR? I'd say the benefits were stuff like throttle tip-in, transient response to load changes, fuel economy, emissions output, combustion temperatures, temperature-related enrichment, ability to control detonation with ignition timing rather than just "lots of fuel", and the ability to use a clear scientific process, making specific changes and empirically validating them across a wide range of conditions in isolation (e.g. changing fuelling at 3k rpms doesn't break fuelling at 5k rpms).

I'm not disputing that at a specific combination of RPM/temperature/altitude you can optimise the mixture using an RRFPR - I just do not think for a second that the car will therefore run perfectly at other rpms/temperatures/densities, especially when using a car operating on fuel/ignition maps programmed for a very different set of injectors, compression ratio, and engine capacity. If you have a logical reason why an RRFPR adjustment is as good as tuning at 2k 4k and 6k rpms under a variety of load conditions, please explain - I'm open minded and if I'm wrong I'll admit it.

When the stroker was built, Devek didn't have the technology to properly tune the car. Part of their job was to manage expectations downwards on things like cold starting, emissions and economy, whilst also putting in enough fuel to ensure no detonation and engine damage. I'm not saying that was a problem - they didn't have any other options available within their budget. I'm certain if Marc and Susan were still doing 928's, part of the stoker-building service would include dyno and sharktuner time.

I guess the difference here is "good enough to meet expectations", and a difference in expectations. Maybe once you get to the bottom of this mess, you could suggest to the owner that he takes it to someone reputable who can attach a sharktuner, put it on a dyno, and tune the car? (with a stock FPR - so it runs from a known fuel pressure and can't be broken with an errant screwdriver in future). It would be a good outcome for the owner and they might once again enjoy driving the car regularly, instead of driving it from issue to issue. Unlike your racer with its chopped up diagnostic wiring harness, plugging an ST2 into an S4 is very non-invasive and easy.

>>>>> i think the dyno shows that the fuel regulator keeps the fuel in the range that is fairly desirable. in fact, bill had the shark tuner meter on the car with the wide bands and saw very acceptable performance for alll ranges of operation . Part throttle and wide open throttle. on the S4 i had 72psi, and 12:5 -13:1. that high pressure might have helped with fuel atomization. ratios were excellent. with the stoker and 30lb injectors, i think the pressure is too low, but it still runs great, albeit on the rich side (11.5 to 12:1) and yes, i think this could be helped by 24lb injectors which seem to map out to sub 400rwhp fine, but its what i got. sure, the shark tune would be great if my wiring harness and ecu were normal.

and sure, emissions and other things could be optimized with the computer, no doubt. more power as well to ability to change timing for different power and RPM settings. but i dont have that luxury. so, it is good enough... and , performance wise, that car rips!!! you can see and hear it, right???? watch the video. no smoke, no hesitation... great smooth power curves... (albeit a few hp less than i would want, but heck, it works!)

with only a 6 liter and stock stuff, the engine and HP is not that much different. i bet a stock set up would have worked, but that's a guess. certainly stock with RRFR would have worked as the power was only what i saw with my stock Holbert S4 5 liter... 335rwhp and good fuel ratios with stock 19lb injectors
all performance parameters were good. off throttle, part throttle transitions

Originally Posted by mark kibort

See my inserts:

<>>>>>>>>>>>>>no , this is not true at all. the o2 sensor makes the closed loop operation possible, so its the feedback to the system and there, you have hunting. more so on the Ljet versions. without it, its not that rich, as it goes to a steady state 12.5:1 or so, and it runs fine... sure emmissions are high, but it runs just fine. ive tested this at the dyno as well, WOT , not effected, and idle and part throttle its just the mixture you would get if WOT .... Im sure you can see more on the shark tuner, but in actually this is not a possible factor unless there was a short or something effecting the ecu via the o2 sensor..

Originally Posted by Hilton

Actually, an oddity of the 928 LH ecu is that if you unplug the O2 sensor on an S4, it doesn't run in open loop mode. The LH only goes open-loop at WOT and high load conditions (high load being defined by combined rpm/MAF signal). If you unplug the sensor, you get increasingly rich as the O2 adjust parameter and adaptation start to drift the wrong way, leading to hunting idle issues. People using a sharktuner to tune circumvent the O2 loop by using a software switch which is analogous to putting the car in non-cat configuration, which uses predefined fuelling maps against a known calibrated MAF signal baseline (calibrated by adjusting exhaust mixture to a known point at hot idle - per Workshop manual).

If this problem 928 has a working O2 sensor and you unplug it, the car will start to run rich pushing the short-term O2 adjust parameter rich, and over time, will get richer still as the slower adaptation parameter started to be affected.

I've never tried to push the o2 adaptation as rich as it will go - its conceivable that it'll eventually get rich enough to cause starting problems, misfires and smoke, but perhaps someone with more experience can chime in? I sometimes forget to plug the O2 sensor back in and only notice once the idle starts hunting, reminding me to plug the O2 sensor back in.

One way to reset the long-term adaptation parameter is to do a battery disconnect. If you disconnect the battery, wait a min and reconnect, does the starting behaviour change? (remember the LH is unfused and powered directly from the battery - should disconnect battery before changing brains regardless)