94 Astro 4.3 220TBI Map trouble

[rentapen]

Per Chilton, MAP reading on VOM 1.5 (or lower) at idle and .5 w/ign off. At ign on, engine off, my reading is 4.75V (ref is 5V ok). I pull map vac line engine runs fine, good inject flow both idle and gunning. With engine running I replace vac line, VOM goes to 2V and the injectors quit injecting engine quits. With the vac line off I can gas it and slowly replace vac line and sometimes it will stay running. EGR (Linear) juice disconnected and TPS test good. Replaced IAC and MAP. Now it get expensive.
Thanks.
rent_a_pen

[old_master]

#1. Get rid of the Chilton and Haynes manuals. They're fine if you're changing oil, after that, they're worthless. Factory shop manual or a subscription to Alldata is the only way to go.

Does the "Check Engine" light come on? If so, what codes are stored? If the light does not come on, the MAP sensor is OK. Check fuel pressure with the engine off and the fuel pump running, then post your results. This should help: http://www.autozone.com/addVehicleId...00c152800a802b

[rentapen]

Thought this forum is for real people not donald trumps. No important codes and check light sometimes. Good flow from injectors could be a tropical conclusion. Replaced filter, used OLD Vac/fuel pressure gage (ain't going to pay 50 bucks for 5 min work) and got 4 pounds pressure. Question, think I can trust the old gage?
Just wandering in Toledo
rentapen

[old_master]

You gotta trust your equipment. If you don't, put it with the Chiltons and Haynes manuals in the trash can. The symptoms that you described point to a fuel pressure problem. If in fact you have 4 psi fuel pressure, that's the problem.

Harbor freight has a fuel pressure tester: http://www.harborfreight.com/cpi/cta...emnumber=92699 $11.00 could save you hundreds in parts, plus your time, (fuel pump costs less than the IAC and the MAP sensor).

[rentapen]

Harbor Fits, "NOT for TBI", could probably be rig'd. The "220" TBI only puts out 9-13 lbs so the gauge must be halfass accurate (I'am reading 4lbs now so the tolerance is of concern) and their $11.00 price is a decent use once store forever price.
Thank you.
To be continued

[CD Smalley]

TBI must be 9-13psi isn't that correct OM?

Some parts store will rent a pressure tester. Call around and see what you can find.

I'm with OM though, you have a fuel pressure problem.

[old_master]

Originally Posted by CD Smalley

TBI must be 9-13psi isn't that correct OM?

Some parts store will rent a pressure tester. Call around and see what you can find.

I'm with OM though, you have a fuel pressure problem.

9psi to 13psi is correct. The Harbor Freight pressure tester does not come with the adapter for TBI, (my mistake, sorry). It might be possible to modify it to fit on a TBI system, but the gauge may not be quite as accurate at the lower operating pressure of that system. Renting the correct tester would be a more viable option.

[rentapen]

Just hooked up the Harbor Fits's gauge (w/Mods) and its results mirrored my 40 year old gauge with one difference, wouldn't you think the Chinese would assume a gas gauge would measure gasoline pressure? The leak down test consisted of the gauge dial filling with gas, whoda thunk. 2 new questions, would a 12psi outside electric fuel pump be easier and faster? If not, what really is the fastest easiest way to drop a tank?
Regards
el cheapo rento

[rentapen]

New question please. Since I hooked my gauge by unhooking my 220TBI I was unable to read pressure while engine was running. Earlier testing revealed 5 to 8 sec test light on, showing juice to my pump, then off. Question, what is the duty cycle of pump. ie; 7 sec. pump on when key is on and then off and then controlled by p'uter after van starts? I dislike to assume anything concerning monies.
Thanks, just wondering in Toledo.