When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
also unplugged o2, after of which car was wanting to stay around 16 afr. from what ive reads when you unplug, it should go rich. So I got mad and ordered one of these
digital fuel or oil pressure sensor. it also has alarm output. So I will either confirm
1. fuel pressure is indeed where it is supposed to be
2. fuel guage I have is innacurate
3. fuel pressure is unstable or not where it should be
4. I have to spend more money
I think in scenario 1, 2, or 3, 4 will be the answer.
i did a fuel volume test. Hose after fuel rail before fuel filter. After 30 seconds. What I read is .75 liter from fuel return line after 30 seconds. So unrestricted, does double that look good?
Looks like this one not sure of brand friend gave it to me. So the pot doesnt signal any enrichment like other motronic systems, only signal for full throttle? Im just wondering why didn't they just use a contact switch for full throttle? That was my theory, if the tps signaled enrichment too that its signal would be lower then normal for the amount of air entering engine causing a lean condition.
See this very long thread from the past, about a car that would go lean despite everything checking out. Based on posts 65 and 69, it looks like that car was using the same FPR you are, and that replacing it with a Bosch 3 Bar regulator solved the problem.
See this very long thread from the past, about a car that would go lean despite everything checking out. Based on posts 65 and 69, it looks like that car was using the same FPR you are, and that replacing it with a Bosch 3 Bar regulator solved the problem.
Ive read that post, it wasn't thexregulatot, or perhaps that was an issue but the problem came back. Turned out the diaphagram in his damper was messed up. I was considering i could have a problem with my damper, its just the original style unit and probably 30 years old, if something is messed up with the diaphagram i suppose it could cause cavitation at certain fuel frequency pulses. Its a cheap enough part to order and swap.
Ive read that post, it wasn't thexregulatot, or perhaps that was an issue but the problem came back. Turned out the diaphagram in his damper was messed up. I was considering i could have a problem with my damper, its just the original style unit and probably 30 years old, if something is messed up with the diaphagram i suppose it could cause cavitation at certain fuel frequency pulses. Its a cheap enough part to order and swap.
It was never entirely clear I agree, but it did seem this FPR was, at a minimum, contributing heavily to the problem. That FPR may depend on more things being "just right" than the bosch. He reported the problem was fixed with the bosch FPR, but then curiously put other parts on the car only to see the problem come back, but never put the bosch FPR back on the car. So to me, that's pretty telling. There's really no point in running that FPR anyway on a VR-equipped 2.5 liter motor -- so would think it very worthwhile and easy to try a standard 3 bar regulator compared to all else you've been trying.
It was never entirely clear I agree, but it did seem this FPR was, at a minimum, contributing heavily to the problem. That FPR may depend on more things being "just right" than the bosch. He reported the problem was fixed with the bosch FPR, but then curiously put other parts on the car only to see the problem come back, but never put the bosch FPR back on the car. So to me, that's pretty telling. There's really no point in running that FPR anyway on a VR-equipped 2.5 liter motor -- so would think it very worthwhile and easy to try a standard 3 bar regulator compared to all else you've been trying.
Not quite as easy, ill have to get some adapter fittings for my fuel lines, try to find my original fuel rail, and get another damper. It has an early rail on it right now.
What's an early rail? Is that something other than a 951 fuel rail?
when i first got car I was having fueling issues, I had the adjustable fpr laying around and decided to put it on as well as being able to see and adjust fuel pressure. I couldn't put it on the 951 rail because of how the stock fpr is attached,but had a fuel rail from an early 944 that was easier to adapt with the fuel line fittings. Hence the early rail. And the damper on my 951 rail was messed up and nut so corroded on that I couldn't get it off.
Tom I think you are on to something. When I did some searching on the 944 forums, the closest thing I could come up with as far as fuel damper causing my symptoms was that thread we both looked at. Everything else described fuel damper symptoms as going rich because sucking fuel into the vacuum line. So I looked outside the box and searched on some other tuner forums. I found alot of references of using combinations of aftermarket fprs and or no/insufficient fuel dampers causing unstable afrs at idle and weird unexplanable going lean issues at rpms between 2k and 3k. And also references of non only rubber fuel lines exaggerating the issue. Rubber hoses have a natural damping effect.
With my system, I have steel internally braided fuel lines going to the fuel rail and to fpr and return, these have practically no damping effect. I dont know the condition of the 30 year old damper on the car. Also something I learned in the fuel industry, fluids change density quite a bit with tempurature. We would go fill up our fuel trucks at the port in cold weather, then park them in side. 980 gallons of fuel cold, when warmed to room tempurature, would turn into 1000, 1020 gallons of fuel, and if we didnt allow for expansion, it would overflow and we would come in the next morning and have fuel everywhere
So im hoping, what im dealing with, is a lack of fuel damping in the lines, plus they are stiff and cold, with a heavier fuel density which increases pulsation effect and an insufficient damper and maybe a fpr that is very sensitive to this.
I could grab the line going to the fpr and feel the pulses pretty good at idle.
I redid the fuel line from the rail to the fpr with a simple rubber fuel hose. I also t'd into this and put a 2' 5/8" hose with a plug on the end, which is in effect a simple makeshift fuel damper. We use the same system on our water pumps in the car wash, and it works good reducing pulsation at 1200psi. This is just a temporary set up for testing. Im hoping when I fire it up tomorrow that I will see some positive results as far as diagnosing the situation. Either that, or back to the drawing board.
Ok i think i the problem was the stiff lines and not enough damping for the injector pulses. I must have had the right combinations of things to create fuel resonating in the rail. So now time to spend money.
I can either get a nice fuel damper add it on and try different fuel lines
Get lindsey rail and mount damper on that, and perhaps 3bar reg adapter.
Might be time to just get a new rail.
Hoping that was the problem.
Macguyver fuel damper test set up.
Sounds like progress! Unless your motor has special needs you haven't discussed, you should seriously just get a stock 951 rail, damper and 3 bar regulator and be done with it. That's what I run on my 500rwhp motor with 044 pump, and I've never had an issue. Just my opinion, but these aftermarket parts all seem to be solutions in search of a problem, at least for most of us. The stock parts are cheaper and rock-solid reliable, so no point in complicating it. I bet Lart can hook you up for peanuts.
Sounds like progress! Unless your motor has special needs you haven't discussed, you should seriously just get a stock 951 rail, damper and 3 bar regulator and be done with it. That's what I run on my 500rwhp motor with 044 pump, and I've never had an issue. Just my opinion, but these aftermarket parts all seem to be solutions in search of a problem, at least for most of us. The stock parts are cheaper and rock-solid reliable, so no point in complicating it. I bet Lart can hook you up for peanuts.
At this point im sure a stock rail will work. I could get the lindsey rail and a damper and probably have it in my car for about 3 Benjamin's. Used stock rail and a 3bar will be 1 or 2 Benjamin's. Sad thing is i had 2 3bar regulators i must have left them in my parts car when I sold it. If you can pull 500rwhp with stock rail im sure I can use stock rail too, nothing internally modified just stage 4 vitesse turbo comes in very fast when it does spool, i don't think I will be running more than 350hp with mods and not planning on going into 20's with boost.
A month ago I had my OE fuel damper go bad, meaning leaking fuel into the vacuum/boost line. Fortunately my (hard) lines are semi transparent, showing moving fluid mixed with air bubbles at idle.
The symptoms were minor, namely unstable AFR at idle (closed loop), running a little rough at low power (also closed loop) and engine restart only taking a fraction of a second as opposed to the typical 2-3 seconds (adequate fumes in the intake manifold).
29 years / 230k miles life span is not bad. It actually was a blessing in disguise, since I noticed that my OE Damper to fuel line connection had developed the dangerous aneurysm. Later design use different and hopefully better rubber material.
A month ago I had my OE fuel damper go bad, meaning leaking fuel into the vacuum/boost line. Fortunately my (hard) lines are semi transparent, showing moving fluid mixed with air bubbles at idle.
The symptoms were minor, namely unstable AFR at idle (closed loop), running a little rough at low power (also closed loop) and engine restart only taking a fraction of a second as opposed to the typical 2-3 seconds (adequate fumes in the intake manifold).
29 years / 230k miles life span is not bad. It actually was a blessing in disguise, since I noticed that my OE Damper to fuel line connection had developed the dangerous aneurysm. Later design use different and hopefully better rubber material.
Laust
I finished modifying my fuel system. I missed a bid for a 951 fuel rail so i decided to make changes to what I have and see what happens.
Im running an early n/a rail. The setup differs from a 951 where, the fuel enters the back of the rail, goes through the damper, and exits also at the rear through the pressure regulator. It has to push the fuel forward to the front of the rail. On the 951 rail its more of a flow through design, entering the front and exciting the back. I got the proper fitting from BAT in Florida and made my rail flow through, entering the rear, flowing through the front, going to an external damper from radium engineering and then to the reg. I may find a better location for the damper but it works for now.
It appears this has eliminated the lean spot. I set fuel pressure at 43.5/44 psi. Idles low 14's. Cruises high 12s low 13s. On boost 10/11.
I did have a hiccup where i was idling at a stoplight and afrs went to 17 sounded like it was stumbling or missing. I revved it up and then was fine.
If my idle is set too low, could my injector duty cycle be at the edge where injectors are unstable?
If you see this john, his far back did your setups have semibatch? Is it possible my vitesse chip is so old it was pre semi batch?
02-15-2017, 03:08 AM
