sqzbox

scenario: Fuel pump is weak or FPR in throttle body go'es bad.
result: Air fuel ratio go'es lean.
Question: Would knock sensor pick up on this causing the ECM to retard the spark timing? At part throttle or wot my timing drops back to 0*. I've eliminated the ignition (every thing but module is new and the module checks out ok) I've got a code 23 and 32 but I think that these are a result of another problem. EGR and MAT system check out OK and one out of 3 manuals suggests TPS could be bad and that the codes pointing at the sensors might be a result of another problem? Hope I get some answers soon as my folical count on top of my head is getting lower from constant scratching and I can't afford rogaine any more than I can afford unessesary parts for my car!!

sqzbox

U think I should post this topic on TBI? I thought Vader would know this one!

five7kid

iTrader: (14)

Getting a fuel pressure gage on it would be a good first step. Monitor while monitoring knock retard.

sqzbox

Yeah, I'm trying to justify buying the fuel P. gauge first being I'm only going to use it 1 time, right? If you think the lean cond. would be heard by the knock sensor, I'll buy the gauge with no remorse! I know it's retarding the timing without monitoring the knock count. You have to remember I'm old school. I've only heard "ping" caused by incorrect octane and too muck adv. in the past. Now my hearing isn't as good and the sound excapes me. I've also heard that the sensor can "hear" what a human can't. BUT! Thats a good idea! I'm going to get a gauge and check it out before I post again. Hopefully my next post will have positive results. THANKS.

Vader

Accordian,

You need justification for buying a useful diagnostic tool? A decent fuel pressure gauge is about a $45 item, with the TBI test adapter. A new fuel pump is about $110. If you choose to have the pump replaced instead of replacing it yourself, the price inflates dramatically. I can only guess the price of a replacement regulator, and suspect it may not be available separate from the TB assembly.

If you suspect a fuel pump or regulator problem, there is really only one reliable method to test them. You could replace both the pump and FPR, but the cost of either one of them is likely well beyond the cost of a test gauge. Using your gauge, you can isolate the problem to a single component, and save the addition parts cost (and still have a tool you can use over and over). You may even be able to trace it to a $10 filter, and save a ton of cash and time/frustration in changing the pump.

Need any more than that? It only makes economic sense to me.

8Mike9

Uh oh...heeeee's baaaaack.

sqzbox

Nice to see you have a good sence of humor Vader!! I got that nick-name (wich is also my CB handle) because I creamed a dumb *** who stoped his car in the middle of the road around a curve on a twolane road in Kentucky one time! (their not to smart down there!). For insurance purposes, pictures were taken at the scene of the accident and the idiots car looked like an accordion!!
Someone at my home terminal posted the pic. on our bullentin board and so U know the rest of the story! Bye the way, I was exonerated thus not held responsible for the accident.
My wife just returned from the part's store with my new FP test gauge kit! ($42.00) Now the fun begins!! and all questions will be answered. I ought to be quite well informed on the subject of fuel pressure and its related problems after all this, and can't wait for the new block of knowlege!!
BTW, I do play a mean guitar!! Martin DM-5 (inherited no doubt)
I couldn't afford one of those either. Next post on this thread will have result's of FP tests. Wife say's I've got yard work to do before I get to play with the car today. Those women have too much bargaining power with their favors don't you know? Thanks for eveyones help so far!!:rockon:

sqzbox

Ok Dudes! here it is. Turned the key on several times to prime and it won't go or hold over 5lbs. started the engine and from fast idle cold to warm idle it won't hold over 7-1/2 lbs. The first thing I did when problem started was change the fuel filter and it made a difference at first but the problem still existed. (dieing after start up, bogging, and poor performance.) My conclusion; after 138,000 mi. I need a new fuel pump! Even with the return line pinched off 7 1/2 lbs is all that it will do! I'm happy to find the problem but dissapointed in the fact that I just put a new rear-end in this spring. Oh well, at least the nuts and bolts will be easier to break loose!

Vader

Yes, you've covered the bases. With the fuel return line pinched closed, you should have been able to make nearly 20 PSIG with a good pump. The only other possiblities would be a failed pulsation damper or leak at the pump pedestal or pickup, and in either case, the tank has to come out. Speaking of the pulsation damper, if it isn't failed, remove it anyway and replace it with a section of fuel hose. You don't need it and the possibility of failure is not worth the risk.

As long as you're certain the filter is good, your analysis should be correct. You do have the option of testing the pressure in the line before the filter just to be certain. And for the cost of a useful tool, you've saved the cost of a regulator and identified the problem.

sqzbox

What's a pulsation damper. And where is it?

Vader

A pulsation damper is a mechanical accumulator that is intended to reduce rapid fuel pressure fluctuations created by the small discharge of fuel from every revolution of the pump. The device is located between the fuel pump and discharge line on the fuel tank insert (lid). Many later vehicles are not equipped with this device, since the noise created by the pump has been "accepted" by the motoring public. There is no other practical purpose for the device, and failures are not uncommon. The rubber diaphragm of the damper can split, tear, or be perforated by the spring, and fuel can leak back into the tank instead of being delivered to the injection unit. In essence, thay are a failure waiting to happen, and cause either a partial or complete loss of fuel pressure when they do occur. You vehicle mat not have a damper, but if it does, you should consider replacing it with a straight sction of fuel hose, as many later vehicles have.

sqzbox

Ok, Good deal. I'll check that when I get it torn down next week-end thaks Vader . Later!

sqzbox

See post "fuel pressure gauge question urgent" on TBI board for results. U won't believe it! I feel sorry for all the people who have taken the long way! YEE HAW!