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1993 Honda Civic Conundrum

My little car will only get sick with me and my support staff (mechanics & son) cannot figure out what is causing the sickness.
I have a 1993 Honda Civic with a mystery malady that my mechanics cannot solve and this issue has been occurring over the last few months. I have figured out if I fill my car to the top (not topped off) it will not start until I let it sit for at least 15 min. The problem continues until the gas level goes down to almost 3/4 of a tank. So I then started partially filling my car and had no problems except in the morning it would not start on first try but always on the second. So I didn’t feel like I would get stranded.
A couple of days ago I accidentally filled my tank too full…not full full, but just too close to the top. It started up and I started out into traffic where I lost almost all power…I managed to limp around the corner to a parking lot where I turned the car off, sat for a bit and then tried to start it again. It started right up and I drove through lot into traffic where my little car totally stalled. There was no starting her:( So in the midst of 5:00 traffic at a busy corner, I put my hazard lights on, put up my hood and then was blessed with a police officer to sit behind me to keep traffic moving.

I was towed to my mechanic where they started the car immediately:( They cannot get the problem to repeat…it is so frustrating. I have two different mechanics trying to figure out the problem and both are mystified. they have said that the symptoms don’t go along with any of the fixes they would normally repair.

Two suggestions have been made and I need more suggestions to help the repair shop. #1…faulty gas cap #2…purge valve

HELP! Mom of Kate Audrey

It’s got a couple valves and an evap control canister with a evap diaphragm. There is a purge control solenoid valve and that is what I would guess. Did they check the fuel pump pressure? I would start there.

Do you ever get a check engine light when this happens?

It’s 20 years old…Time to start planning for the future…

“Too full” tells me you are topping it off when you fill up.

DON’T DO THAT!!!

First, this is an “OBD 1” emissions car, so there is no fuel tank pressure monitoring. This started in 1996 with OBD 2 emissions. So topping it off shouldn’t matter. But there is still supposed to be pressure in the fuel tank. When you take off the gas cap is there some pressure released? There should be. Make sure it’s pressure being released, not vacuum, which I’ve seen once. you could leave the gas cap loose to see if that helps. I would be monitoring fuel pump pressure, as suggested. Knefimore’s diagram of the evap system is good, you could disable it to confirm if it’s the problem. Good luck.

Conoso, the fact that the presuure isn’t monitored does not mean that topping the tank off won’t saturate the charcoal canister and prevent the gas tank from breathing.

However, in this case I’d start by checking for fuel pressure at the line. Having to wait 15 minutes suggests to me that the fuel supply needs time for “head pressure” (from the weight of the fuel" needs time to refill the fuel line before there’s enough supply for the car to restart. A weak pump would also be the cause of the car stalling.

In short, this sounds to me like a dying pump much more than it sounds like an EVAP system problem.

I’ve been following this trying to make sense out of it. So far every suggestion made, which are the same things I have been thing of, but would be aggravated by low fuel level, not high fuel level. But SMB just triggered a thought, bad fuel pressure regulator.

Its a quick check, just pull the vacuum line off the end of the fuel rail and if gas comes out, you need a new regulator.