Fuel Pressure Up VSV

[jetjock]

Btw CyFi6 asked a question in that thread and considering this one me thinks it and the answer may be worth repeating:

What does running the fuel pump before starting up do? Wont the vapor, if there, just stay there, don't you need to apply vacuum to the regulator so it opens up and purges the vapor? Just not sure if i am missing something.

Look at the TRSM procedure for checking fuel pressure. If you jumper the pump (engine off) what does pressure go to? Does it go to a value that indicates the pump is in relief? A pressure that indicates the pump is being dead headed? No, it doesn't. Where do you think pressure is being relieved?

The spring in the regulator is calibrated to maintain fuel pressure (without a vacuum bias) at 33-40 psi. The GTE uses Toyota's Type A injection system. The spec for that is 36 psi across the injectors. Note that value falls midway between the 33-40 psi speced in the TRSM for a regulator check. The regulator isn't closed when the engine is off and the fuel pump is on. Under those conditions it's doing exactly what it was designed to do: regulate fuel pressure at 36 psi. Of course, it does that by bleeding fuel (and vapor if present) back to the tank...

 

[CyFi6]

JJ - you posted in the thread he's referring to...

Completely different issue in that thread...lets put it in context:
http://www.supramania.com/forums/showthread.php?85039-poor-idle-after-warm-restart

In addition, this is the "complete" post I made:

If you're going to take a shot at me, be a man and post complete info. Editing out part of what I really said in a post and completely out of context is simply unsat...and, a cheap shot.

I'm not trying to start a war here, but my statement was that if fuel pressure isn't held in the rail, it can cause the fuel to boil, and your statement was that I was wrong; it had nothing to do with the fact that it was cold outside, hence why I didn't include the part you bolded.
I left the actual quotes there so anyone could click on them and see the entire thread, there was/is nothing I am trying to hide. Are you implying that I made a legitimate point, but because it was cold outside where Grim lived, it made my comment idiotic? According to your statement, vapor lock would not be a possibility, even in Silver MK3's situation. In fact later in that thread more than one other person suggested that Grim fix his rest pressure issue just in case there was a vapor lock problem. This is not an attack on you, this is an attack on your info, just as you did to mine.

 

[jdub]

I'm not trying to start a war here, but my statement was that if fuel pressure isn't held in the rail, it can cause the fuel to boil, and your statement was that I was wrong; it had nothing to do with the fact that it was cold outside, hence why I didn't include the part you bolded.
I left the actual quotes there so anyone could click on them and see the entire thread, there was/is nothing I am trying to hide. Are you implying that I made a legitimate point, but because it was cold outside where Grim lived, it made my comment idiotic? According to your statement, vapor lock would not be a possibility, even in Silver MK3's situation. In fact later in that thread more than one other person suggested that Grim fix his rest pressure issue just in case there was a vapor lock problem. This is not an attack on you, this is an attack on your info, just as you did to mine.

Then why not quote everything I said? Instead you removed 3 short sentences that changed the context - typical of your passive/aggressive shots at me.

What you were telling him to do was leading off on a tangent path that had nothing to do with Grim's real problem - and, you wouldn't stop. I didn't say he shouldn't fix fuel pressure, in fact, the part of my quote you chose to edited out said he should fix it. Just like JJ said above, once the pump is up and running, the fuel rail is purged of any vapor. That's why vapor is a start problem - primarily when it's hot outside, not an idle problem. In Grim's thread, you just didn't get that, and that's what made what your info idiotic in that thread - a very basic lack of knowledge how the fuel system works.

 

[CyFi6]

Then why not quote everything I said? Instead you removed 3 short sentences that changed the context - typical of your passive/aggressive shots at me.

What you were telling him to do was leading off on a tangent path that had nothing to do with Grim's real problem - and, you wouldn't stop. I didn't say he shouldn't fix fuel pressure, in fact, the part of my quote you chose to edited out said he should fix it. Just like JJ said above, once the pump is up and running, the fuel rail is purged of any vapor. That's why vapor is a start problem - primarily when it's hot outside, not an idle problem. In Grim's thread, you just didn't get that, and that's what made what your info idiotic in that thread - a very basic lack of knowledge how the fuel system works.

Because what you bolded/what I had taken out didn't change my argument at all, and didn't affect the point I was making - I don't see how it changes the context, if I saw that it changed the context I would not have removed it - it's that it had nothing to do with my argument. Again I am not trying to attack you or take shots at you, it is what you posted that I have issue with.

Then perhaps I still don't get it. You are saying a vapor lock problem will only cause the car to not start up (I think). Silver MK3 is complaining of a rough idle immediately after a hot restart- the exact symptom Grim had.

I think it is the fuel pressure up vsv, because when you start it when it is hot, and pull the vacuum line from the vsv off of the fuel pressure regulator the idle instantly rises and smoothes out, and when you put it back on the idle drops to below 500 and it gets really rough.

what would cause a very poor idle after a warm restart? it idles off the charts lean and misses along with right above 500 rpms for idle. Once i start driving and egts increase (above 500 degrees f) it smooths out and no issues even at idle. revs fine and only area that you can notice the issue is idle right after the start.

if i let it cool off enough to go through cold start enrichment its perfectly fine. o2 is new (bad heater circuit), no codes, plugs have maybe 2000 miles on them.

i searched but the 3 letter limit has me playing with the wording to get good results...
no exhaust leaks, valves are within spec, new coolant csi time switch, timing is set per tsrm, fuel pressure is normal etc, let me know what you think or what else i can test. would the ecu's coolant temp sensor cause something like this?

dont know if this is related. After decelerating using the engine as a brake and i push the clutch in the car idles right at 500 rpms before it works its way up a bit to the normal 650 rpms. Only does this after is fully warmed up and been driven a bit.

I guess I don't see how these are completely different issues, they sound very similar.

 

[IndigoMKII]

:1zhelp:

 

[Silver MK3]

Thanks for all of the help and information guys, I definitley appreciate it. I just ordered a new vsv to replace my old cracked one. I figured that while it is off I might as well replace it since it is cracked. Once, the new vsv gets here I will install it and see if it fixes the issue. I will also try jumping the fuel pump on before I try to start it hot, and see if I do have a rest pressure problem like you guys suggested.

JetBlue 191 may have an opening for one of you two. :icon_razz

I am confused about this whole thread. Didn't he state in post #1 that pulling the vac line off the FPR caused it to run better? Seems like it could be the FPU, but then all his tests say its working okay??

Yes, pulling the line of of the FPR does casue the idle to smooth out and run better, that is why I thought that the FPU VSV was the problem. When the vsv was tested though, it passed all of the tests. One thing that I thought is, maybe when it the VSV is hot, the crack may expand, or so and cause the VSV to not function, but when it is cool(it was cool when it was tested) it functions perfectly and passes all of the tests.

; THA > 60C & THW > 100C or
; THA > 75C & THW < 95C
; command FPU on

What exactly is this, and what does it mean?

 

[3p141592654]

What exactly is this, and what does it mean?

See here for a better explanation...
http://www.supramania.com/forums/sh...bly-Analysis&p=1823168&viewfull=1#post1823168

 

[Silver MK3]

I got the new VSV in today from toyotapartseast.com. Hopefully I will get to installing it sometime this weekend, and find out if it has been causing my hot start problems.

 

[Nick M]

I am confused about this whole thread. Didn't he state in post #1 that pulling the vac line off the FPR caused it to run better? Seems like it could be the FPU, but then all his tests say its working okay??

High fuel pressure can over come a few different problems. Or stated more correctly, hide the problem when the mixture is easier to light.

 

[Silver MK3]

I replaced the VSV last sunday, and so far I have only got a hot start problem once during the week, and it really wasn't that bad. The car just idled at 500 for a little while, but once I gave it some gas it was fine. It didn't do what it was doing before with hardly being able to keep running and stalling without giving it gas. I will keep an eye on it and see if this has solved the problem, or if it didn't do anything. Thanks again for all the help.

 

[Nick M]

Do you also have the original fuel pump?

 

[Silver MK3]

Do you also have the original fuel pump?

Yes, as far as I know it still has the original fuel pump, unless the original owner changed it but I doubt that.