Vsv

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billsheila

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The online FSM located via this site is for a 2002 4Runner. I own a 1999 SR5 with the 3.4 V6. The fuel pump inspection section discusses a VSV which is apparently a Vacuum Switching Valve that is involved in the so-called "Fuel Pressure Up System" common on Toyota's. This system is aimed at reducing the possibility of vapor formation in the fuel rail after a hot soak...this latter item being the problem I think I am having with my engine.

Does anyone know, does a 1999 have a VSV and this related "Fuel Pressure Up System". Attached is a scan of two documents. First is from the 2002 manual and it mentions the VSV. Second page is from a general description of toyota fuel systems that I found on the web, also mentions the VSV and its purpose and operation.

Question: Does a 1999 4Runner have a VSV? If so, anybody have any idea how to test it or find it? I couldn't find anything in the FSM on the VSV, but I may have just missed it.

Thanks in advance for any help.
 

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Well I looked some more in the manual, and found some more data on the VSV, it shows it near the gas tank at the back associated with a charcoal canister. I just went out and crawled under my truck...I don't seem to have such a beast. My evap system is all under the hood, and none of it seems hooked up to my fuel pressure regulator (but it is hard to get to the regulator and see exactly what is going on there).

So are we sure that there are no changes between a 2002 and a 1999. Does anybody have a manual applicable to specifically the 1999 model year?

This whole issue of hot soak vapor lock, I wonder if it was an issue on the early 3rd gens and then they changed the system in the later 3rd gens? Anybody else got any insight here?
 
I have the '99 FSM. My page SF-6 is identical to the page SF-8 that you posted. They did move the charcoal canister between '99 and 2002. I don't know enough to answer your question about 'fuel pressure up' and 'hot soak'. I can't find any mention of a 'fuel pressure VSV' anywhere other than the sentence you posted. There is only the 'vapor pressure VSV' that is on the EVAP charcoal canister. One suspects some translation imprecision in these cases. Hope this helps...

That VSV is right on the canister under the hood and has three hoses going into it. To test it, remove it, and check that the resistance between the two terminals is between 37 and 44 Ohms and both terminals are isolated from the body (i.e. show no continuity). Air should flow from the center port to one side with no voltage on the terminals, and then flow to the other when 12V is applied.
 
Thanks TheDurk. I think "hot soak" means "when engine is restarted after being hot, and has not yet cooled down". By the description of the fuel pressure up process, it seems on some toyotas they have recognized this hot soak problem (where fuel has vaporized and can vapor lock the fuel rail). I am pretty certain this is the problem I am having.

But I can certainly test the vapor pressure VSV that you point out so thank you for that information..I think this one has more to do with vapor pressure in the gas tank than the fuel rail, but I will give it a look and see. My next step I think is to rig up a fuel pressure tester so that I can see what is going on with fuel rail pressure during a cold start and a hot start etc. If it is a vapor lock issue in the fuel rail, I have no idea how to fix it, but it should show up (I think) as unstable fuel rail pressure during a hot start.

I have not changed the fuel pressure regulator as yet, so that may be the culprit, and others have suggested to me that even though the pump has been changed, it may not be putting out enough pressure (ie a bad replacement pump basically), which might be causing the issue.
 
What did i break now?

Is this the vsv? 1989 4runner 4cyl 4x4
 

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Is it safe to start up? can i drive it like this to work tommorrow? (my only car) if anyone knows the specific name or part # that would help a lot....
 
1989marty said:
Is it safe to start up? can i drive it like this to work tommorrow? (my only car) if anyone knows the specific name or part # that would help a lot....
Click to expand...

Those actually look like the 4wd vacuum switches I have on my 97... But I'm unaware if there is any similar thing on the 89...

I would test out your 4wd and see if you can both engage and disengage 4wd..
 
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