Fuel pressure issue?

[rb0095]

For a long while my car has been hard to start. It does not seem to matter if it is cold or hot. In adjusting fuel/air mixtures, checking for vacuum leaks, and other things that I have tried to solve this issue I may have found something.

I noticed that when I turn the key on (without staring the car) the fuel pump also turns on for a brief second, that seems normal. The thing that I am concerned about is that during the time when the fuel pump is on the fuel injectors (all four of them) also spray a little fuel into the engine. Is this normal? (I replaced all the fuel injectors in early 2009 so I would think they aren't the issue)

If it is normal I am surprised...if I were to turn the key on/off the back on multiple times I could flood the engine (just like stepping on the gas petal too much with a caborated engine).

[Briano1234]

I am not a CIS guru, but the Fuel pumps do run for 4 seconds at key on. This is to pressurize the fuel lines.

At no time should the injectors weep fuel in to the engine. If they are leaking that is a problem.

I defer to the CIS junkies and their love of that fuel distributor.

[rb0095]

I am not a CIS guru, but the Fuel pumps do run for 4 seconds at key on. This is to pressurize the fuel lines.

At no time should the injectors weep fuel in to the engine. If they are leaking that is a problem.

I defer to the CIS junkies and their love of that fuel distributor.

Thankyou, that's what I thought, but was not sure...I guess I'll be looking into why the fuel injectors are spraying prematurely.

[gull]

Off the top of my head, things that could cause the injectors to spray fuel with the engine off:

- Airflow meter plate not returning to rest position
- Worn-out injectors
- Bad fuel distributor
- Maybe excessive system pressure? That would cause other problems, though.

I'd start by checking the AFM plate. Maybe you have some crud in the AFM bore that's keeping it from dropping all the way down? The injector spray should cut off cleanly when the plate is all the way down -- you can stuff the injectors in a glass bottle and jumper the fuel pump to run continuously, to test. An occasional drip is OK, anything more indicates a problem.

[gull]

Also, once you fix this you will probably need to re-adjust the base mixture.

[rb0095]

...Maybe excessive system pressure? That would cause other problems, though...

What other problems would that cause?

When I first got the car (October 2008) it was not running due to leaking fuel injectors. They told me that it was leaking fuel so bad that there was fuel coming out of the oil dipstick. The fact that fuel was in the oil in the first place makes me wonder if the fuel pressure has been an issue for longer than I have had the car. After buying it I replaced the fuel injectors, so I wouldn't think they would be bad already...

I would need to get a fuel pressure gauge to test pressure, do you know where I can find one?


I now also remember that when I bought the car the fuel pump relay was not working properly so someone had rigged it so that when the key was on the fuel pump was running. The fuel pump relay has been corrected, so that shouldn't be an issue.

I'll look into the airflow meter plate, but last time I checked it seemed to be working properly...then again I wasn't looking for a problem.

Also, once you fix this you will probably need to re-adjust the base mixture.

Up until recently I have been constantly adjusting the mixture to keep the car running well...it never gets much better, and never makes a difference on how it is starting; re-adjusting is expected. I have finally decided that I am going to fix this issue once and for all, that way I won't have to be constantly adjusting things.

- Bad fuel distributor

How do you test the fuel distributor?

[gull]

...Maybe excessive system pressure? That would cause other problems, though...

What other problems would that cause?

Poor running due to incorrect mixture.

I would need to get a fuel pressure gauge to test pressure, do you know where I can find one?

JC Whitney used to sell one, but I can't find it now. This looks like the same item, but it's on the pricey side. Someone may know of a cheaper option.
http://www.tooldesk.com/automotive/ATD5 ... -Only.aspx
You really can't diagnose these systems properly without testing system and control pressure. If either of those are wrong, adjusting the mixture will only move the problem around.

- Bad fuel distributor

How do you test the fuel distributor?

[/quote]

It's mostly a process of elimination. They almost never fail and they're expensive, so you want to check everything else first.

[rb0095]

Ok, I just did a quick check of the afm, even when I push the afm plate down as far as it will go, it still sprays a little fuel when I turn the key on (fuel pump runs for a second to prime lines, also causes fuel injectors to spray).

One other question, excessive fuel pressure would also cause the car to get poor fuel mileage right? I don't know how many mpgs a 1.6 is supposed to get, but right now I am averaging about 27 mpg.

$90+ for a fuel pressure tool is a lot....but so far it would seem like I may be needing it. Would be a bummer if I got it and didn't need it though. I'll keep checking other things...if I can.


A 1.6 engine (when using a dwell meter) should be adjusted just like a 1.8 right? When I adjust the fuel mixture I usually follow this process http://cabby-info.com/cis.htm. Is it possible to have the mixture adjusted incorrectly and still get the right readings on the dwell meter?

[gull]

If you plan to keep working on CIS-injection VWs, you'll need it again sooner or later. Look at it this way...it's cheap compared to shop labor.

I have no experience with the 1.6L, but I would expect it to be the same.

27 mpg actually sounds about right. My guess is the mixture is correct when the oxygen sensor system is active, but incorrect on start-up when the system is not yet functioning. I've seen that before.

[rb0095]

If you plan to keep working on CIS-injection VWs, you'll need it again sooner or later. Look at it this way...it's cheap compared to shop labor.

Decided to go ahead and get one. I found one for a little less here: http://www.sjdiscounttools.com/ta33865.html and it comes with a case

Thanks for the help thus far.

[gull]

No problem...let me know if you need any help interpreting the results.

[rb0095]

After checking the afm I noticed the car was not running like normal...turns out I forgot to clamp down the airfilter box properly.

More importantly, while checking to see what was wrong I found a vacuum leak (I thought I got rid of all of them...) The leak is coming from the throttle body. One of the screw things that holds a valve in the tb is letting air in. I've been looking around to see if there is a gasket or something (maybe an o-ring?) that can be replaced to fix the leak, but can't find anything. Anyone know about fixing thottle body vacuum leaks? (it is not leaking from idle screw...just replaced that o-ring)

I don't think this is the cause of my issue, but it certainly isn't helping...

[Briano1234]

Try wrapping that screw with about 3 wraps of teflon tape.

[eric4321]

Are you refering to the cold start injector on the passenger side of the intake or the actual throtle plate? You might be able to get away with silicone on the cold start injector but I don't have enough experience with cis to know for sure. You may also want to check that cold start injector as well they are prone to leak from what I have ben told.

[rb0095]

Are you refering to the cold start injector on the passenger side of the intake or the actual throtle plate? You might be able to get away with silicone on the cold start injector but I don't have enough experience with cis to know for sure. You may also want to check that cold start injector as well they are prone to leak from what I have ben told.

No I am not referring to the cold start injector. I have checked the cold start injector for leaks and as far as I can tell it is not leaking.

Try wrapping that screw with about 3 wraps of teflon tape.

I'll take a look at it...see if I know what you're talking about.

Further tips on fixing my vacuum leak or fuel injector issue are welcome.