Ok, so my car wont' stop stalling when in gear at a dead stop. I think alot of you have seen my earlier posts.

I got stuck in an hour long traffic jam yesterday and lets just say Im wondering if it is the pump.

I don't understand the whole "oil pressure relay" and how the TPI pump gets power. Nobody in the electronic section has been able to shed any light on that.

Basically, at first my car idled for like 5 minutes, move 5 feet forward, sit for 30 seconds, move 5 feet forward etc. Typical snail pace of a traffic jam. It stalls. I start it back up, it stalls a little while later. After 30 minutes it goes from stalling periodically in gear to just not being able to hold gear at all. I have to shift from neutral to drive over and over again, prob 100+ times over the next 30 minutes. Whereas at first I could idle in gear for a little while before it shut down, restart and idle a little while, now as soon as you were at a dead stop in idle it stalled. So it would hold in neautral for a while. Then after a while it got to the point where it would not hold idle in neautral either and was just stalling out. I have 18PSI of oil pressure at idle. My car was fully warmed up when I got stuck in the jam. As time went on it just got less and less time before it stalled. Then it would not even hold in neautral (thank *** I cleared the traffic jam right as it started stalling in neautral)

I got out of the traffic jam, and magic, it just drives PERFECTLY, granted when i come to a stoplight 5 min later i have to throw it in neautral and rev to keep it from stalling but it DRIVES perfect, just won't idle. Now either someone can explain to me WHAT is causing the fuel pump to die out, or i have a some sort of problem with my engine other then fuel delivery. The idle mixture is set, the floats are set correctly. Basically, I'm looking for someone to tell me yes that my fuel pump is indeed giving out and im losing power from . I'm looking for someone to tell me def that it's a power supply problem or im buying a new car. I can't take this anymore....i can't keep spending money replacing part after part and getting no results. I just can't do it, i spent another 600$ yesterday, im 1000$ in debt, i can't keep pouring money into this thing with no result. I'm not looking for guesses anymore, i'm looking for anyone who has seen this before. I personally can't make heads or tails of it, the engine runs so well mechanically, EVERY part of the induction system is brand new. Distrib, wires, plugs, carb etc etc. I changed my spark plugs to a colder range with no change at all in my idle quality.

It just makes no sense, the car used to stall after 15-30 seconds, and it has been lasting longer and long, the car beings to stall if your in gear at a dead stop, i can feel it start to stumble, if i take my foot off the brake at that moment it recovers. maybe i do have too much compression.....maybe i do have a vacuum leak....or maybe it is the fuel pump. Again i have no idea what to do to the pump. What do i do? Rip the carpet off from behind the back seats, cut the fuel pump power line, and run a direct 12v feed from the battery to the pump? I can't buy anymore new parts....thats it, i can rewire the fuel pump and find out if thats the problem and im done. if that doesn't fix it im done with this car.

originally when i let the car stall in gear and checked the float it looked dry, however i found out that the float is supposed to beonly SLIGHTLY above the sight glass when set correctly, so no, there was still some fuel in the float, so i dont' even know if the bowl was bone dry.

 

How the FP gets power:



Fuel demand is greater under load than at idle. Having prolems at lower RPMs and no problems while driving would tend to negate your theory of a failing fuel pump. To be certain whether the pump is functioning, you should test the fuel pressure.

 

8PSI of pressure coming out of the 3 port regulator. Consistent, this is with the key in the "ready" position. I don't understand how the wiring works, I have the chiltons guide and I don't exactly follow how the power works.

As you mentioned, it makes no sense my problems are in idle. However someone told me that if something is wrong with the oil pressure switch relay that the fuel pump would cut out in idle. I was also told that electric motors don't run unless they are getting "optimal" voltage. Meaning if my pump is only getting 85% voltage, that it may only be running at 25%, that performance drop is not equal to voltage drop.

Basically, is there something between the fuel pump and it's power source that could cause it to cut out ONLY in idle. If it's not fuel delivery then it makes no sense, at least if it's a fuel problem I can fix that.

From that diagram I can gather that the pump gets power from either/or the fuel pump relay side and the oil pressure switch side. Which side is supplying power when the engine is on? I mean, a damaged relay would simply not work. Oil pressure switch? I again don't see how oil pressure shoudl affect how much power the pump gets. I mean, when the car is running, the pump NEEDS 12vs of power ALL the time right?

 

My 88 form LO3 wouldn't run worth a darn at 7 1/2 lbs. Starting problems, no power, bogging all that stuff! Put a new pump in last week-end and got 13 1/2 lbs. now. Run's great!

 

Stealth,

What engine/fuel system are you running? You mentioned a "three-port regulator" and "carb" in your text. Most carburetors get along just fine with 3-5 PSIG of fuel pressure. Some carbs can't tolerate over 5 PSIG since the inlet needle will unseat under the pressure, flooding the engine.

 

Mallory 3 port regulator.

stock TPI pump

670 holley street avenger

took my 305 TPI out and put in a carbed 350

 

Now it sounds like vapor lock, Huh? I always thought perf. eng. w/Holley needed at least 7lbs at WOT through the rpm range. But I could be wrong!

 

Yea, my buddy says it sounds like vapor lock, but it's stock fuel setup, we just took the original TPI lines that run next to the driver side strut tower and hooked up the regulator. The line is nowhere NEAR the headers...we checked that.

I would believe the fuel cutting out if it consistently cut out, but it doesn't.

I think it might be possible that my float is flooding, though when I let it sit in gear at a dead stop in a driveway and let it stall, then took the sight glass off, the float didn't leak, if you take the sight glass off, and turn the fuel pump on, the fuel SLIGHTLY trickles out of the sight glass hole, which is where it should be, SLIGHTLY higher then the sight glass. So it makes no sense.

I'm a little calmer now then when I made that first post. Tomorrow we're going to re-track the power supply going to the pump and make sure I have adequate power. Then we're going to put a T into the fuel line and check fuel pressure AGAIN and vacuum again. Just basic tests for the pump, if that doesn't fix it....oh well, I'm done.

 

Stock don't mean nothing. My dad had a 56 chevy wagon with a six banger that we used on many vacations. When the weather was warm and going up-hill with a load it would stat bucking like a horse and as soon as we stopped it would die. It was my job as the young one to jump out with a wet rag and cool the fuel line down for a couple of minutes and then it would re-start and run for a while. I've seen this happen on vehicles with metal fuel lines and on my car too. I've got around this problem by using rubber fuel line in place of metal. If you think it don't look cool, put some braid on it. The line doesn't have to be near anything hot, just the under-hood temp's are enough to cause vapor lock, especialy in traffic. I'm not saying this IS your problem, just don't rule it out. Third Gen. has a hard time getting heat out from under the hood. I've got the door off my form. power bulge just for that reason. Not cooler air in, but hot air out.

 

The reg wasn't hooked up yet, but you can see the fuel lines in the bottom right corner. We just took those stocker lines and connected them to the reg.

 

To answer some of your earlier questions, yes, the fuel pump needs a constant 12 VDC when the ignition is on.

If you suspect the fuel bowls are dry when the engine stalls, remove the air cleaner and observe the primary bores/venturis while you operate the throttle linkage. If the bowls are dry, you will not get an accelerator pump shot into the bores. If you get a pump shot, you have fuel.

Since you're using a 3-port regulator, the chance of vapor lock is minimized. The pump will force a relatively constant volume of fuel through the system and regulator, relieving any excess back to the tank. This would tend to displace any boiled fuel back to the tank, and render vapor lock nearly impossible. "Vapor lock" is a condition that occurs most commonly on engines that use a block-mounted mechanical pump, whereby fuel in the suction line from the tank is boiled so that the pump essentially loses its prime and cannot move any more liquid fuel. A system that pumps liquid fuel from the tank under pressure (like yours) is almost completely immune to true vapor lock. It just doesn't happen that much on modern engines.