CIS Testing Sans Engine

[1982911SCTarga]

Just an update. I re-checked the pressures again and there was no change. Also, I think there is fuel seeping from the center plunger, which leads me to suspect the fuel distributor is in need of a rebuild/recalibration.

I've got a spare fuel distributor on hand from my supply of squirreled-away CIS components, so I'm going to hook that one up and see if it's in-spec vis-a-vis the pressures.

Brian

[boyt911sc]

Brian,

You're lucky at this point that you have a spare FD on hand. What will you do next after putting this new FD and find out that the system pressure is still LOW? You'll be back to square one!!!! If I were you, I'll determine the fuel pump delivery pressure or rate (liter per min.) before doing any further troubleshooting. Check the following: (1). Pressure or delivery rate after the pump, (2). Delivery rate after fuel filter. This is the fuel rate going to the fuel distributor. (3). If there is a significant difference in the flow rates between (1) and (2), you got a problem. Let's see what delivery pressure or flow rates you have. Good luck.

Tony

[Tim Hancock]

Originally Posted by 1982911SCTarga

Just an update. I re-checked the pressures again and there was no change. Also, I think there is fuel seeping from the center plunger, which leads me to suspect the fuel distributor is in need of a rebuild/recalibration.

I've got a spare fuel distributor on hand from my supply of squirreled-away CIS components, so I'm going to hook that one up and see if it's in-spec vis-a-vis the pressures.

Brian

Don't know what to tell other than that IMO, a leaking center plunger will not affect the system pressure reading (control pressure...maybe, system pressure....no). The pump is capable of putting very high pressure, which is simply relieved/regulated by the spring controlled pressure regulator on the FD, it allows excess fuel to return to the tank anytime the fuel pump is running. Unless your center plunger is spraying fuel all over the place when the pump is on, I doubt it would have any affect on the "system" pressure.

[1982911SCTarga]

Tim, I pretty much agree with you. The small amount of leaking wouldn't account for the system pressure being off so much. Something is going on, though, that is dropping the system pressure way off from where it should be. When I disassembled to check the pressure port on the current fuel distributor, I think there was only one spacer (pressure) shim in place. I dunno how many are usually used. Maybe someone's monkeyed with the shims?

I'll hook up my back-up fuel distributor and see if that makes a difference with the system pressure. If it doesn't, then there's troubles somewhere in the fuel supply and return lines, or possibly in the gas tank. However, I've seen no indication of gunk, buildup, sediment, rust, etc., so far.

I have to get my targa re-inspected tomorrow, too. My parking brake light saga.

Brian

[Tim Hancock]

Brian, it sounds easy enough to hook a couple lines to the new FD for testing, but if that doesn't solve it, you simply need to cob up a pressure gage to test for pressure prior to reaching the FD. Scrap hose, hose clamps, old fittings.....whatever it takes to get a simple pressure check. I would say you are getting close to solving this mystery. I assume you have laid your eyes on some CIS diagrams because refreshing up on them really helps me when trying to troubleshoot my CIS systems (at least for a short time periods, my CIS system has actually been crystal clear in my head ).

[1982911SCTarga]

Another update: I was able to deadhead around the control pressure (warm-up) regulator with my CIS gauge to check system pressure. I did this by connecting the CIS gauge to the center-front port of the fuel distributor and to the rear port which is normally reserved for the control pressure regulator return line. I got system pressure on the original fuel distributor and new fuel pump of 70 PSI. That's right in the heart of where my system pressure should be.

I'm thinking now that there's a blockage of some sort in the return line between the control pressure regulator and the fuel distributor that's screwing with the pressures when the control pressure regulator is in the circuit.

By the way, I was ready to test out my spare fuel distributor and -- go figure -- the center piston is stuck.

Projects ... one step forward and two steps back.

Brian

[boyt911sc]

Brian,

Good to hear you're making some progress. It will be very helpful to other readers following your saga if you attach some pictures (pressure gauge attachment). At this point, do you know what CIS component/s might be the problem if any? Have you checked the cold control pressure? Keep on the good work and your car will running pretty soon. Good luck.

Tony

[1982911SCTarga]

Keep on the good work and your car will running pretty soon.

Thanks, Tony. I think a time assessment of "pretty soon" may be a little generous in my case. Still every little advancement helps. Was it Mao who said that a journey of 1,000 miles begins with the first step? I try to do something each day/evening, even if it's only a few minutes.

I've got to start digging into the condition of the engine, clean and reseal it and the transmission, and do a number of other things before everything goes back together.

The system pressure was bothering me because if I couldn't nail it down, the next steps would have been the fuel tank and fuel lines, which is really something I didn't want to have to get into. So it looks like I'm OK on that front. I've also confirmed that the cold start valve (the seventh injector) doesn't weep, so that's another item to slide into the "good-to-go" category.

My personal timeframe for getting project cabriolet back on the road is May-June-July -- and that's with having everything sorted and corrected, including body/paint issues and air conditioning.

Brian

[Jim Williams]

Brian,

It sounds like you have already learned a great deal about CIS and your system in particular. I apologize that I have not read every post here in detail. If you have not already found my CIS website, you may find some info there that would be helpful. Other posters have made some good suggestions.

See http://members.rennlist.com/jimwms/CIS/CIShome.html

I can confirm an idea you had early in the thread about hooking up a test bed. I did this very thing a few months ago to test my system before installing it on the engine. I mounted only the fuel bearing components on a roll-around cart and pushed it into the engine compartment (car on a lift), then connected the fuel lines, a pressure gauge, injectors in Frappuccino bottles, and measured away. You can use a Mity-Vac for a vacuum source.

Let me know if I might be of some help.

[1982911SCTarga]

Jim, thanks, and thanks for all of the information you've made available to us non-CIS haters.

Brian