Faltering acceleration

[KHE]

The fuel pressure for the TBI engines should be the same as a carbureted engine - 9-13 psi. If the car has been sitting for five years, it's possible the line from the filter to the TBI unit is gummed up and possibly the injectors also.

If the fuel pressure is below 9 psi, you need to plumb in a shutoff valve on the return line, then jump the pump and slowly close the valve on the return line. The fuel pressure should rise above 13 psi, if not, the fuel pressure regulator is bad.

If you pull the vacuum hose off the fuel pressure regulator, does fuel drip from the regulator or does the vacuum line smell like fuel?

[drchamp]

KHE, after four days with this problem you hit the nail on the ahead. I disconnected the fuel line between the in-line filter and the TBI. Fuel is flowing out of the in-line filter just fine. So I blew on the line going to the TBI and it felt like there was a little if not a lot of restriction, this was done with the fuel line in the TBI disconnected. So I tried blowing back the other way from the TBI towards the in-line filter. It felt like something gave a little and the back pressure wasn't as bad. So I reconnected the line at the in-line filter. I then stuck a hose on the line at the TBI end and stuck the other end into a gas can. I turned the key to on and fuel was just flowing out of there. I reconnected the line at the TBI and started the car up. It started right up, had full power and ran for about one minute and died. Took both connectors off again and tried blowing through the line again and it was deftly restricted. Looks like it only happens in high fuel demand. Got to find somebody with a compressor so I can blow the line out really good. If that doesn't get it going to replace the fuel line between the TBI and the in-line filter. All I can say is thank you 1000 times and I love this board. I'll come back and let you know how this works out.

[KHE]

KHE, after four days with this problem you hit the nail on the ahead. I disconnected the fuel line between the in-line filter and the TBI. Fuel is flowing out of the in-line filter just fine. So I blew on the line going to the TBI and it felt like there was a little if not a lot of restriction, this was done with the fuel line in the TBI disconnected. So I tried blowing back the other way from the TBI towards the in-line filter. It felt like something gave a little and the back pressure wasn't as bad. So I reconnected the line at the in-line filter. I then stuck a hose on the line at the TBI end and stuck the other end into a gas can. I turned the key to on and fuel was just flowing out of there. I reconnected the line at the TBI and started the car up. It started right up, had full power and ran for about one minute and died. Took both connectors off again and tried blowing through the line again and it was deftly restricted. Looks like it only happens in high fuel demand. Got to find somebody with a compressor so I can blow the line out really good. If that doesn't get it going to replace the fuel line between the TBI and the in-line filter. All I can say is thank you 1000 times and I love this board. I'll come back and let you know how this works out.

It sounds like there is some crud blocking the supply line from the filter to the TBI inlet based on your description. I would disconnect the supply line from the TBI and force shop air from the filter end of the line to force the blockage out. You may need to eventually replace the entire line if you can't clear the crud from the line.

[drchamp]

Well I finally replaced the line between the in-line filter and the motor where it meets the metal line. I then had good flow to the end of that line and when I connected it to the metal line which was clear, I got about two PSI to the TBI. I said a few choice words and went to Napa and bought an AC Delco pump. Wow what a difference, I have all the pressure I need to the TBI now. Tried starting the car and it would not fire up. I then remembered when I rebuilt the TBI I also put a new diaphragm in the pressure regulator. I pulled the metering cover off with the pressure regulator. Took the regulator apart but could not tell if it was leaking because The diaphragm moved on me while disassembling it. I put a thin coat of silicon sealer on the metering cover side, placed the diaphragm on it and put it back together minus the spring for the night. Next morning I put the regulator together put it in the TBI and started the car. It now idles great and I can run the RPMs up with no faltering. The only problem I have now is when I tried to drive it up onto ramps (under heavy load) it faltered again. Let it sit for two minutes and it started back up. Anybody have any ideas why it falters under heavy load. I still think I need to replace that pressure regulator but I thought I'd ask here before I go and spend money I don't have to. Thanks again for all the help and I'll log back on tonight to see if anybody had any suggestions.

[KHE]

When you put the car up on ramps, what is the fuel pressure reading?

Is the fuel pressure regulator external to the TBI unit? It should be on the return line. In post #26, I described how to test the fuel pressure regulator.

[drchamp]

First I'd like to thank everybody on this board for the help I received with this problem. I ended up replacing the complete fuel line from tank to engine compartment metal tubing. I also dropped in an AC Delco fuel pump. Car started to run like a champ so I took it out for a test drive. I made it about 15 to 25 yards and the engine died. Checked the fuel pump and I could not hear it running. So I had a friend drive and slowly poured fuel into the carburetor to get it back into the yard. Dropped the tank again and found the new AC Delco pump was bound up. Like a dummy I didn't put a sock on the pickup tube. This forced me to stick my hand down in the tank and see if there was anything in their. To my surprise I found a bunch of rubber particles and black rubber dust in the tank. Then I remembered the first pump I took out had the blackest sock I had ever seen on the fuel pump. So now it's down to taking the tank off and send it out for an acid bath or just buy a new tank. I opted for buying the new tank and be done with it. So what was happening, while driving the fuel was mixing with this rubber type dust and making its way to the throttle body. Bad fuel, bad performance. I'm chalking this one up to experience and thank everybody again for the help.

[Bruce Nunnally]

12 minutes ago, drchamp said:

First I'd like to thank everybody on this board for the help I received with this problem. I ended up replacing the complete fuel line from tank to engine compartment metal tubing. I also dropped in an AC Delco fuel pump. Car started to run like a champ so I took it out for a test drive. I made it about 15 to 25 yards and the engine died. Checked the fuel pump and I could not hear it running. So I had a friend drive and slowly poured fuel into the carburetor to get it back into the yard. Dropped the tank again and found the new AC Delco pump was bound up. Like a dummy I didn't put a sock on the pickup tube. This forced me to stick my hand down in the tank and see if there was anything in their. To my surprise I found a bunch of rubber particles and black rubber dust in the tank. Then I remembered the first pump I took out had the blackest sock I had ever seen on the fuel pump. So now it's down to taking the tank off and send it out for an acid bath or just buy a new tank. I opted for buying the new tank and be done with it. So what was happening, while driving the fuel was mixing with this rubber type dust and making its way to the throttle body. Bad fuel, bad performance. I'm chalking this one up to experience and thank everybody again for the help.

Thank you for the report.  Sounds like you have the right diagnosis, and a good path to correction.