Trouble Tuning

[ctuinstra]

Recently during tuning for new fuel injectors and the boost-referenced fuel pressure system, I ran into trouble trying to get a good tune. I won't bore you with all of the details, but fuel AFRs were all over the place and I just couldn't get anything to work half way as expected. I did notice during the tuning that something was making a high-pitched squealing noise when the ignition was turned on, thinking it might have been the intercooler pump or something, I would check it out later. At one point I finally noticed my fuel pressure during priming was 90PSI!!! I had the regulator set to 4Bar (58PSI) originally. Adjusting the regulator had no effect. I removed the return line going back to the fuel pump and ran it to a gas can and the pressure dropped to normal. So I knew it had to be something in the fuel pump assembly. This fuel pump is new and was installed last fall because the original failed to start up every time.

This is what I found inside the fuel pump. The return comes in on this gray plastic housing which holds the original ball and spring regulator (the ball was remove previously to omit the pump regulator). Inside this housing is a small filter screen to filter the fuel returning to the pump. It was 90% clogged! I can only assume this was debris left over from the manufacturing of the new fuel lines, regulator, fittings, etc. I cleaned the screen and put it all back and it's working great again and I'm getting much better tuning results.

I doubt others will run into this very often, however I found it interesting.

 

[JeffsGoblin]

Chad, what pump is that? AC Delco? MU2221? Glad you found the issue!

 

[ctuinstra]

Chad, what pump is that? AC Delco? MU2221? Glad you found the issue!

I don't remember exactly. I typically try to buy OEM if it's reasonable, so most likely an AC Delco.

 

[ctuinstra]

Well, one tank of gas and the filter is clogged again! Not really sure where the debris is coming from. I may have made a mistake and installed a 40 micron fuel filter inline instead of something that would filter smaller particles. I'm looking into using a 10 micron filter now. If that doesn't do it, it has to be coming from the lines or fuel pump.

 

[George]

Can you take a picture of the debri?
Brad

 

[ctuinstra]

Can you take a picture of the debri?
Brad

It's so small and embedded in the screen. It would be difficult to get out of the screen to collect it. With spray cleaner, it cleans out easily.

 

[George]

It sound like it is coming from the fuel, yes a finer filter would be a good start.

Brad

 

[George]

I worked on a BMw a while back that had fine rust floating in the fuel. I I shined a light in the tank you could tell it was cloudy. It would clog the main fuel filter in two days. The main filter should be finer than the screen in the return.
If you install a 10 micro filter carry a spare for a while.

Brad

 

[Desert Sasqwatch]

Stupid question: did you clean/rinse out the fuel tank and fuel filler tube before assembling and installing the pump? The fuel filler tube has a black coating that comes off and can get into the tank. I found this a while ago and posted to clean the tube with gasoline and a rag pulled through it. I hope this is not the problem, if so the tank probably has this stuff floating around inside.

 

[George]

Fill a Mason jar with fuel from the tank hang a strong magnet in the fuel and see if it collects anything.
Brad

 

[ctuinstra]

Stupid question: did you clean/rinse out the fuel tank and fuel filler tube before assembling and installing the pump? The fuel filler tube has a black coating that comes off and can get into the tank. I found this a while ago and posted to clean the tube with gasoline and a rag pulled through it. I hope this is not the problem, if so the tank probably has this stuff floating around inside.

That's a good thought. I did not clean the tank, ever actually. I figured the filter on the bottom of the fuel pump would take care of most of it but I guess it's not a very fine filter.

So obviously I didn't have this problem before, so looking at the changes should lead me in the right direction.

1. The OEM filter was removed and a different type installed. Potentially with a larger particle filter size.
2. The return was from the OEM filter back to the pump. Very short path, out to the filter and back.
3. Now the fuel travels all the way up to the fuel rail, out the rail to the regulator, and then back to the pump.
   1. Could be picking up particles in the new filter assy and new plumbing, but fairly unlikely
4. We could be picking up particles (such as the hose debris) from the tank.
   1. That may have been filtered out by the original OEM filter before returning to the pump
   2. Since we don't know the particle filter size of the OEM filter, I have to assume it's best case senario.
5. New injectors
   1. Possibly, but highly unlikely, picking up particles from injectors and backflowing in to the fuel during shut down.
6. Fuel system was opened
   1. Could have picked up something from the bench, rust, corrosion, etc. while open to the elements.

I've ordered the following:

https://www.jegs.com/i/Aeromotive/027/12347/10002/-1?trk_msg=67FB60CGH39457V504JLOLSL0G&trk_contact=K69DTCP423JV10BI8V85CM9V14&trk_module=tra&trk_sid=JGSPD93IV6DHIMLS4QO0J5V2SS&utm_source=listrak&utm_medium=email&utm_term=Product&utm_campaign=Transactional&utm_content=Order+Confirmation

I'm going to leave the screen in the return port to see if this problem continues. Just makes me wonder about the injector spray. I may have to have them flow tested once I feel this has been resolved.

 

[Lonny]

Is your pump self destructing?

 

[George]

The injectors have replacable screens, most do any way. The main filater should be the finest. I ca check spray pattern and compare flow rates if you have a reason to come to KC

Brad

 

[ctuinstra]

Is your pump self destructing?

I was actually wondering that myself as I was typing the last response. That's a great question.

 

[ctuinstra]

The injectors have replacable screens, most do any way. The main filater should be the finest. I ca check spray pattern and compare flow rates if you have a reason to come to KC

Brad

I'm going to investigate that on my old injectors. I will feel much more comfortable with this new 10 micron filter. I don't know what the OEM filter is, but I could not find anything better than 10 micons.

I will be making monthly trips to KC again when things settle down a bit and I may very well take you up on that. If nothing else, piece of mind.

 

[ctuinstra]

Lonny could be right. It might have been the fuel pump going bad and eating itself. The car left Kaleb stranded (in town thankfully). No fuel pump. No pressure. I had to leave work and grab the trailer and bring it home. Going to check into to see for sure tonight.

It’s a new fuel pump and I checked, I bought it just over a year ago and it’s the AC Delco OEM pump (MU2221).