1G Gas Smell and Bad Mileage

[MackZ24]

I'm trying to diagnose a problem I've been having with my 91 AWD A/T for some time. There is frequently a strong gas smell in/around the car, and I've been getting very poor mileage. (It used to be ~130km/tank, that's only about 80 miles for all you guys on the imperial system)

I knew my timing was way off, so I've recently set it back to where it should be (~5 degrees btdc). I also have tightened down all the fittings on my AFPR (Aeromotive compact version), and all the AN fittings connected to my fuel rail, etc.

I'm running -6AN braided line right from the tank, to an Aeromotive fuel filter, again from the filter to the rail, and from the opposite side of the rail to the AFPR. The base pressure has been set to 43.5psi, as per factory specs. for an automatic car. There is also a Walbro 255HP fuel pump installed in-tank.

The O2 sensor is nearly-new, with less than 1000km on it. The car runs and drives very well, idles fine, and boosts without issue. I haven't done a real "recent" BLT on the car, but I will go out and do that now, just to be sure.

The only other things I can think of that could be affecting this, that I've checked out are the TPS, which is only off by about 1-2% when the car was last datalogged. When I have access to a tuning laptop again, I will make sure it's dead on. Also, the EGR valve has been blocked off/removed. BOV is recirculated. Spark plugs are brand new as of last weekend. Air Filter is *maybe* 3 months old. (Other than what I've mentioned, the car is basically stock, except for 3" turbo-back exhaust).

I know the car is running somewhat rich, but I'm not sure why. A co-worker has let me know on occasion that there is some black smoke out the tailpipe when I go WOT with him behind me. But as for the gas smell, is it possible that I've got a leaking injector? Does anyone have any other ideas?

Thanks in advance!

 

[ramsack]

if you're still running the 390s then the stock fuel pressure is 42.7 psi. that will save you a tiny bit of gas, but 1 psi difference isn't going to make a huge gas smell. you probably have a leak somewhere in your fuel system. does your fuel pressure go down when you leave the car sit? you can lose a lot of gas with a tiny pinhole leak that won't even create drops, but just a vapor.

 

[90moneypit]

This could be really simple. Have you checked the gas tank for leaks? Look at the rubber fuel fill elbow on the drivers side for leaks. The car is almost 20 years old and it's the first thing to check. From there start checking all the fittings and lines running forward from the tank since you replaced them all with braided (how long ago?) and it IS possible for them to be damaged. Otherwise, did any of the other symptoms start right after changing something? You just changed the plugs, what did they look like when you pulled them?

 

[MackZ24]

ramsack > Sorry, that was just a typing error on my behalf, the fuel pressure as you stated, is actually set at 42.7psi (or as close as I could get, judging by the gauge on the AFPR). My fuel pressure has always bled off once the car is turned off. But I searched a while back and there were others having the same issue with Aeromotive AFPRs at the time? Also, it's not as bad as it used to be. It used to bleed off immediately, because of a torn O-Ring on the fuel pickup, but I've now ran a piece of hose with clamps, and that problem is no longer present.

As you say, there are no visible liquid leaks anywhere, is there any easy way I can try to track down a vapor-only leak? Or is my only option to pretty much replace each section of hose and see if it's fixed?

90moneypit > As mentioned above, there are no visible leaks, but obviously since I can smell it, vapors are escaping somewhere. Unfortunately, I did all this work to the car (pump, AFPR, braided lines, etc.), before it was on the road, so I can't say whether it would have started happening after any particular mod or not. Also, the plugs I pulled didn't actually look too bad, a little bit of a tan tinge to them, but they were running in the car when the timing was set *way* off, and the O2 sensor was shot, so I didn't expect them to look very good.

 

[ramsack]

to find a leak like that you gotta get under the car with a flashlight. you can see it spraying out, but most times it won't form drops on anything and just vaporize into the air. did you remove the charcoal canister or anything like that? my sending unit is only being held on by 2 bolts out of 6 and the gasket is shot so gas spills out of my car on windy roads. also make sure the fpr is good and not dumping gas into the vac line.

 

[Killerclipse]

I've had a problem with my 2g leaking gas after I put in my new pump and upgraded to 6AN lines. There's a gasket (grommet?) that goes between the lid you screw on and the tank. My car wreaked of gas and I could see gas on top of the tank. I had to take the it out, let it dry since it was soaked with gas, put it back on, tightened the lid back down and the problem went away. Don't know if it's the same with 1gs, but you might check the top of the tank for a gas leak.

 

[90moneypit]

^Beat me to it. I was going to recommend checking that gasket between the sending unit and the tank if you can smell it on the inside of the car. It's a 20 year old piece of rubber too. I'm not sure if it's even available to buy anymore either. You might want to try the dealership for that one as they'll probably be the only ones who'll know for sure if it's still available.

A question about all those AN fittings, did you properly wrap them with teflon tape during the install?

 

[Killerclipse]

I've checked the OEM section on JNZ and I couldn't find it

My next stop is a junkyard or a Mitsu dealership.

 

[ramsack]

if you have an advance auto around, then they have the gaskets. it's part number 68206 and it's made by bosch so it's oem. that's bosch's part # too so you may be able to look elsewhere for it.

edit: i also just thought, how did you connect the line back where the sending unit is? if you were able to get the stock fitting loose, and used an AN fitting to go right to the stock hard line that will leak. AN fittings are 37 degrees flare, and the one on the sending unit is 45 degrees. if you used an npt or some other threaded fitting without a proper flare it will leak.

 

[MackZ24]

ramsack > The charcoal canister has not been removed (at least, I don't *think* I removed it, but I will double check). But since you and others have mentioned it, the rubber gasket between the gas tank and sending unit/cover was definitely gone. I used some RTV around it, to try and get a better seal last time it was apart, but perhaps I didn't use enough and should remove it and either find a new gasket or try again with more RTV. Even still, would this not sealing properly cause such horrible gas mileage?

I will also double check the vacuum line running to my AFPR to make sure there is no gas getting into it.

Also, the connection at the sending unit goes into an NPT-to-AN adapter, and then the AN line is threaded onto that. (Yes, the NPT connection to the adapter has been wrapped with Teflon tape as well!)

90moneypit > Perhaps you meant connections with regular pipe threads, rather than AN, but I don't believe you should be using Teflon tape on AN fittings. AN fittings seal with flares, not through the threads. But yes, on any standard thread fittings (such as to the AFPR), they have been wrapped with PTFE. I also just replaced all the PTFE last weekend when I was making sure all connections were tight, and that I wasn't getting a leak from them!

 

[SrKegler]

Check the hose and clamps for the fuel return line from your AFPR. Mine was leaking there. Definately a gas leak someplace though.

 

[ramsack]

For starters you don't want to use teflon tape on AN fitting threads. The threads in the AFPR seal with an o-ring. Also i don't follow exactly what you did at the sending unit with fittings. The only place you should use teflon tape is on the gauge going to the AFPR, that SHOULD be the only NPT thread in the whole fuel system. Teflon doesn't dissolve in gas, it's just not wise to use it on fittings that will be coming on and off often, as it can leave threads of itself in the fuel system then.

Can you offer up pics of what you did at the sending unit with fittings? The tank gasket won't hurt your MPG really, but it will make everything smell like gas. Don't use RTV, use the gasket that's made for that.

 

[90moneypit]

I'm not overly familiar with the AN fittings other than my experience with the AFPR so I'll take your word on it. As far as using RTV on anything that will come in contact with gasoline, DON'T! Gasoline dissolves RTV, it's one of the things you use to clean a part that HAS RTV on it. The only stuff I've found that has similar properties to RTV is Seal-All. It's slightly rubbery so it'll fill in gaps, just make sure to let it cure before re-installing. I'd recommend putting a bead around on one side, let it cure, apply bead on other side. Worked for me but I'll be looking into the Bosch gasket for a more permanent replacement myself.

*Thanks for the part # ramsack!*

 

[blakktalon]

I know you mentioned it earlier, but did you ever check the injector seals? if one is slightly ripped it will have a small leak, the only way to tell is to take off the fuel rail and look.

 

[DSM1G90]

Do you still have the stock 390 injectors and if so, the thing is running pig rich, for the Wally 255 is way too powerful for those 390's. That Wally is actually pouring tons of fuel in the bores....

390's are made with the stock fuel pump. Wally 190's are more compatible with stock injectors since they're not as powerful.


Good luck-DSM

 

[yepes281]

Check for boost leaks, if you know your running rich then that could be it. The higher the rpm the more air the ecu is expecting so it injects more fuel. If you have a leak then theres not enough air but all the extra fuel and yea you get my point. Mine smells like gas when i have a boost leak.