91 4runner starts then stops.. HELP

[wdiceo]

I have a v6 91 4runner. Starts and then struggles and dies.

backstory. bad battery was casuing it to be hard to start, but it always did. One day wouldnt. Tinkered... had battery replaced. Starts and then stops. Thought fuel pump, replaced. Thought filter. Replaced. Still the same. So, stopped being an idiot and got the dealer tech manual. Did a check on the fuel pump, connected fp to b+, essentiallybypassing the relay to the Air Flow sensor and whatever else in there that controls current to the fuel pump.. works fine. I can start it up and it runs normal.... so I tend not to think vacumn leak or EGR problem.. Only thing; ive now repalced the air flow meter... still the same problem..

What should my next step be? And am I correct in assuming not vacumn leak? If I bypass the relay and hook fuel straight up.. it starts right up.. no hesitation... I havent run it long like this since im not sure if its bad on the truck.. but it runs fine. Idles, oil comes up.

HELP. Its been a two week project at this point(work full time)...and im miss my baby.

Are there fuses or relays somewhere that my bad battery might have shorted? or have gone bad?

[Brian R.]

Welcome to the AF!

Have you checked for codes in the ECM?

Check your fuel line pulse damper by the firewall. It may be leaking. A common problem with that engine.

Try cleaning your EGR valve.

[wdiceo]

Thank you.
Well, I have not checked for codes.. but only becuase I thought a check engine would come on?

Not? Ill check it tommorrow...


Fuel damp... well I smell no leak, I will look, but Im assuming since It runs fine with the relay bypassed that there is no mechanical a.k.a cold start clog or throttle problem..

I could be wrong, im new to all this and learning as I go.

[Brian R.]

You're probably right, but all these are easy to check and eliminate as contributors or indicators.

[chachy6959]

You may also want to check you fuel pressure regulator. Just replaced mine which fixed a multitude of intermittent sins and improved gas mileage dramatically. I now get 19-20 mpg rather than 12-15

[4Wheel]

IF as you say the engine runs fine with the fuel pump "jumpered" then the fuel delivery should be OK.
Focus on the fuel pump enabling circuitry. I have had to run a fuel pressure gauge while driving to see the fuel presure drop out.

[4runnerdent]

I also have a 1991 4runner that does the same thing. Did you ever find out what the problem was?

At first it would not idle, but would drive if I pumped the gas. I've completely removed the VAF and intake hose, and now it will idle for approx 10 seconds but will not respond to gas anymore. What's the deal?

Thanks for any help!

[OzzyO]

4Runner Dent if your having the same problem, try starting a new Thread or Post about it , since this Post is so old most people might not be reading what you Replied with.
I have no idea what it could be Sorry But If You Posted a New Thread, You Will Probably Get An Answer.
Also try The FAQ And The Toyota Manuals the First 4 Posts on every page, they have alot of good information there.

OzzyO