CIS Testing Sans Engine
 

I'm working through some fairly profound CIS issues with my '83 cab project. Before I removed the engine and transmission, I ran preliminary system and control pressure tests, which both indicated low pressures. I replaced the fuel pump with a new unit that I keep as a spare and the low pressures were little changed.

Troubleshooting for low pressures continues on with blockages in the fuel lines (checked OK) and clogged fuel filter (checked OK). Meanwhile, the accumulator checks out.

What I did discover on removal of the engine and removal of the fuel injection gear was a potentially sticking fuel distributor piston. I've carefully cleaned the piston and the bore with carb cleaner and the piston now slowly drops after its pushed up into the bore.

The warm-up, or control pressure regulator, appears to be new and I have service receipts backing that up. However, because of the low system pressure, it's difficult to assess if it is working, or can work, as it should.

In the background of all this is a broken wire on the cold-start valve switch. The cold-start valve provides an additional shot of fuel at start up. When I bought the car, it was leaking abundantly and the oil was strongly contaminated with fuel.

What I "think" happened was with the cold-start valve inactive, the car was difficult to start -- cranking and cranking without much action but meanwhile the crankcase was getting loaded with fuel, to the point where it began leaking as in an overfill situation. There was oil/gas in the airbox and gummy residue on the air sensor arm, etc.

So I'm cleaning all that up and with all of these details I've outlined, here's where I am: I'm thinking about reconnecting the CIS components in the engine bay (sans the engine) in order to again check system and control pressures, flow rates and check for leaking/bad injectors, including the cold start injector (for leaking/dripping). The reason I would like to try this is so that I have some confidence that on the full re-install of the engine and transmission everything is good to go. Is this a workable idea? Granted, I wouldn't be hooking up anything electrical, but at least I would know I'm in the ballpark with basic specs.

Brian

CIS Trouble Shooting......
 

Brian,

This is the reason why I built this jig with the help of my son to troubleshoot CIS motor before installing in the car after a rebuilt, repair, etc. Everything is ready for SC motor ('78-'79) mount and start. For later SC motors, additional wiring for the oxygen sensor might be needed. You are more than welcome to utilized this jig.

http://forums.pelicanparts.com/uploa...1193676381.jpg
http://forums.pelicanparts.com/uploa...1193676410.jpg

Now to answer your question, it is not practical to test your complete CIS without the motor. Why? You need electrical connections and vacuum lines too. You cannot tell if any of your CIS component is deffective or not without running the motor. Assuming that you're able to test the CIS (complete unit) sans the engine which is doubtful, and it still does not give you assurance that it will be trouble-free when the completed engine is installed in the car.

Unlike when you have a running motor that has been bench tested and run repeatedly that could give you confidence and assurance that everything is OK. And trouble shooting and fine tuning is very convenient with this set-up.

Tony

Hey, Tony, thanks for the help, and nice setup you've got there.

I understand this, which is why I'm only pointing to reconnecting the CIS to get a basic pass/fail, same as if one were doing cold pressure tests with everything installed in the engine bay. If you do this with the engine in the car, the engine isn't running, so there's no vacuum going on. There's also no electrical power to the warm-up, or control pressure, regulator because it's disconnected.

The idea is to: Could I not simply pressurize the system (by operating the fuel pump) and then apply 12 volts to the cold start injector to check its operation and pattern?

My main concern focuses on the fuel distributor and my out-of-whack low system and control pressures. I'd like to have that nailed down before I put everything back together.

Brian

Seventeen views? Where's the love for CIS? :D

Just as a reference, here were the initial pressure numbers: Brian

Another basic approach would be to deadhead the incoming and return fuel lines near the firewall (near and behind where the filter and fuel accumulator live) with my CIS gauge. That would provide a rough approximation of system pressure, right?

Brian

I've read at least one thread where a CIS car had issues due to varnish in the fuel head rendering the piston immobile - this was detected by the air flapper not moving at all with the system pressurised. Although there should be some resistance due to the fuel pressure, this apparently felt solid...

You could ignore the vacuum stuff for now, hook up the fuel system components and check to see if the cold control pressure has changed now that you've cleaned up the piston in the fuel head.

If it has, I think you have perfectly good justification for expecting that warm control pressure will be similarly changed, no? I don't know if just running the WUR heater element until the control pressure stops changing is a good enough test of warm control pressure, but it'd probably give you an idea.

The low system pressure is a worry - I think there's a pressure regulator in the fuel head itself (or in the fuel pump on some years?). Perhaps that's also sticking and needs cleaning?

You can certainly check the fuel pump flow rate with the motor out, testing it in situ gives the green light to all the lines, filters etc. as well as the pump.

This would also give you an opportunity to see if any of the injectors leak, although a professional cleaning and flow-test them might be a good investment.

If the exercise enables you to locate only one thing that's harder to rectify with the motor installed, it's worthwhile, I think. And your point about raising the confidence when the motor is re-installed is good - you'll know the CIS checks out, so wouldn't have to waste time chasing that down.

Far as the CSV goes, I ran all last winter with the thermo-time switch disconnected altogether, and car started great - in fact, rather better than it does now, with it connected (although other things have changed)... I'm tending towards the opinion that it's really not needed until the temps drop significntly below freezing...

I agree with you, spuggy. I think I an hour or two spent on a "dry" CIS run would be appropriate, in at least confirming that I've got good system pressure and cold control pressure. I'm not sure about the cold start valve issue. I might be dealing with a stack of issues here, such as the sticking fuel distributor plunger, the previously non-working cold start valve or more (possibly one or more dripping injectors or dripping cold start injector).

What I do know: The engine was rich running (wet, oily spark plugs) and it was overfilling with fuel-contaminated oil. The few minutes that I ran the engine, it smoked like hell, but idled remarkably smoothly. By the way, I made sure the engine wasn't hydrolocked when I went about that.

The only other bad signs so far are some carbon buildup (I've seen pics of worse), on cylinder intake No. 2. The intakes on the other cylinders all look clean inside.

Brian

I had a few minutes to look in the engine bay last night and it's a plumbing nightmare (adapt this to that to this ...) to simply deadhead the supply and return fuel lines with the CIS gauge. It looks like a simplified reinstall (no engine) and test of the CIS is in order.

Brian

Should be easy enough to check for dripping injectors if you attach the CIS and pressurize it. And even a rudimentary pattern or flow-test should be enough to spot gross problems that need further attention.

The sticking plunger may well have been the only thing wrong, but why not check/inspect/clean what you can whilst it's easily accessible? I see no downside... :D

I soaked 6 injectors fully submerged in injector cleaner for 24h and checked the flow with the help of 6 small glass jars; worked good.
I wonder if you could fill the line to the fuel distributor with injector cleaner, then pressurize and free the sticky plunger?

System Pressure....
 

Brian,

Slide back the engine back into the engine bay and do the test. All you have to do is hook up all the fuel lines back, install CIS gauge kit, and run the fuel pump. You can measure your cold system and cold control fuel pressures this way.

And if the cold system pressure is still low, there are two (2) things to double check: FD pressure relieve valve and fuel pump delivery pressure. But before doing the test, measure the delivery fuel pressure after the fuel filter to acertain sufficient flow to FD.

Keep us posted and will find the problem.

Tony

Gunter, I think I've got the sticking center plunger resolved, but the test hook-up should tell me for certain.

One could pressurize the fuel distributor with air, as well, to release a stuck plunger. However, I would advise being extremely careful doing so. The plunger is a work of art and any mishandling, rough treatment, etc. could potentially and permanently damage it.

Have you hugged your CIS today? ;)

Brian

SC Engine Test Stand
 

Tony -- would you be willing to share some photos and design drawings for that engine stand you built? I've got a '79 SC that I would love to run on a stand like that. My garage is in Richmond, possibly you would rent it to me for a month or so?

Thanks, Duane

Engine Test Stand......
 

Duane,

I'll be more than happy to see someone make use of this gizmo. PM me for the details like address and tel. # to contact you. I also need to know what kind of oil circulating system on the motor for correct plumbing.

This is a direct bolt-on for '78-'79 SC motors with headers/SSI exhaust. For motors with stock exhaust, a different oil line extension going to the oil tank is used. For later SC motors - no wiring for the oxygen sensor installed yet.

Tony

Last evening I cleaned up all of the CIS lines and the air flow sensor. I've still got to clean/degrease all of the intake runners and the airbox, but my plan for now is to re-mount the fuel distributor to the air flow sensor and connect up all the lines for the in-engine bay testing of system and control pressure, injector leaking/dripping, injector spray patterns and delivery volume comparisons.

Brian

Brian, for the low system pressure, I would investigate the fuel pressure regulator located on the fuel distributor. It employs a spring that attempts to hold a plunger closed. Under normal conditions, it cracks open just enough to maintain the system pressure. Excess fuel is directed back to the tank. With the fuel pump running, it does not care if the injectors are flowing or not, it simply regulates the pressure of the supplied fuel prior to being utilized by the FD. It could be stuck open or some shiite could be holding it open. I personally would start with checking that. If you take it apart, be careful not to lose any shims that may be installed under the spring (that is how the pressure is typically adjusted).

Tim, thanks. I've been thinking about what you've mentioned and I was hoping I wouldn't have to go in there. My gut, however, tells me this bears investigation for the reasons you state. I'll open up that pressure port this evening and report on any scheiss I find in there.

Brian

The fuel distributor pressure port was clean as a whistle -- no scheiss at all in there. The small piston, O-rings, etc., all looked good, so I buttoned it back up.

After a hundred or so Q-tips, I've got the air sensor plate unit neatly cleaned up, so I'm ready to reassemble and re-test the pressures. I've still got to clean the throttle body, air box, intake runners and related hoses, but I can confirm that there's the potential for a live, working CIS under all those layers of oil, dust and crud. :D

Brian

Well if system pressure is still low, sounds like your fuel pump may be taking a crap. I had one just like it in an old 924 that uses CIS and it would pump enough pressure to run, but not well. When I pulled the pump out and tapped it on the ground, flakes of metal came out with the remaining fuel in it.

This pump would still make flow rate prior to the FD when pumping to atmoshere, but it would not make system pressure.

When I started that troubleshooting job, I did not have a CIS pressure tester... by the time I finished, I had made myself one ;):D.

Tim, yes, a bad fuel pump is high on the list of causes of low system pressure. In one of my earlier posts, I swapped in a new fuel pump and the pressures were little changed, so that's why I'm on to checking the more obscure things.

I'm close to checking the pressures again. I've got everything hooked up, but my battery needed to be charged overnight. Updated pressure results coming soon ...

Brian