Bosch Fuel Pump on Spica System

[pete]

Just had an educational experience that might be valuable to others.

I installed a Bosch pump to replace the original on my 1750 Berlina; works like a charm with no modification to the system. Delivers more than the .6 gpm recommended by Ingram and I've not seen the low press light except for the split-second at start. The pump outlet is straight as opposed to the 90 degree on the original; the stock rubber line was a bit short and tried to kink because of the large bend required so a longer replacement is recommended.

As noted elsewhere on the board, pump diameter is slightly smaller so it won't fit the bracket without a little "wrapping".

The "education" came from discovering that the fuel tank was loaded with rust crumbs and some blobs of junk that clogged the pickup tube from tank bottom to outlet, resulting in intermittent and unpredictable fuel starvation. Relined the tank using the Kreem tank liner process; easy to do and effective, cost about $55.

You gotta love old stuff!

John
'66 Spider
'69 Berlina

[Roadtrip]

Glad to hear the L-Jet supply pump is working good. I'm a little surprised that you don't get a fuel low pressure light on the battery only. With a L-Jet supply pump retrofit it's recommended to narrow the fuel restrictor to 1/16" vice the 3/32" that's standard. I've tested both ways with a fuel pressure gauge and came up with the following values:

Standard Restrictor:
5-7psi on battery with intermittent low pressure light
10 psi on alternator

Narrowed Restrictor:
10 psi on battery
15+ on alternator

If you start feeling any loss of power or hesitation on hard accels or long inclines, you may want to narrow the restrictor. I know Wes says as long as the low pressure light is out, you're good to go, but my personal experience has shown that the injection pump likes a 15 psi fuel feed better than 10 psi.

[pete]

I actually had a 1/16" restrictor in there to begin with because I experimented with a non-Alfa pump. Immediately after installing the Bosch pump I got an annoying squeal from the the pressure relief valve. Removed the restrictor, the squeal disappeared, and I've put about 400 miles on it under varying conditions without problems.

My pressure test guage crapped out but I'll post some system pressure data on this installation for a comparison.

John
'66 Spider
'69 Berlina

[genericwood]

I have been unable to make my car run right since installing one of Wes' modified pumps. As others have mentioned, Wes said that the fuel supply shouldn't be a problem as long as the low-pressure light is working properly. But now I'm wondering if the problem isn't the later Bosch pump I'm using? Once the snow melts and the temperature rises, I might have to try a smaller restrictor in the return line as recommended here.

Hmmmmmm?

Erik Wood

[Roadtrip]

Erik - What's "not right" about the way the pump is running? Are you getting symptoms of mild fuel starvation during long inclines? Hard acceleration?

As said before, the difference between a 3/32nds restriction and a 1/16th restriction is about 5 psi from my experience. No need to wait for Spring. Just unscrew the front fuel fitting from the injection pump, clean it off real well with solvent, and let dry. Take an ordinary propane torch and melt some electrical solder over the existing restrictor, then drill a 1/16" hole and replace the fitting. Takes about 20 minutes tops.

[genericwood]

John, the main symptom I have is just a lean condition. When I first installed the pump from Wes, I could not get it to run rich enough. It had a miss that got worse at high revs and the car wouldn't run at all about 5500 rpm. A plug check shows a really lean condition. BTW, it runs great in the garage with no load. After working with Wes (through email), I eventually traded the pump back to him for a replacement. When it was installed, the problem was still apparent. I haven't had an opportunity to set the mixture properly yet with the new pump, though. One the weather improves and I have time, I will try swapping out the pump (I still have the original) or reducing the size of the restrictor.

If that doesn't solve the problem, I'm not sure where to go next. I have been all the way through the ignition including taking off the MSD.

Erik

[Roadtrip]

OK, I think I remember your previous posts on this.

Be methodical with your approach to troubleshooting. Changing more than one thing at once will just confuse you. I'm pretty darn sure that the rebuilt pump Wes sent you is good. I'd doublecheck EVERYTHING else before blaming the injection pump. I forget, do you have an Bosch L-Jet Supply pump (inlet-outlet fittings in alignment, not "L" shaped like the older Bosch/SPICA suppply pumps) installed in place of the originals? If so, I'd start by doing the restrictor mod. It doesn't cost anything, is quick, and reversible. Putting a T fitting in the line between the front filter and the injection pump will allow you to specifically check the fuel supply pressure. Did I send you the guide I wrote on the fuel supply system? If not, send me an email address and I'll email it to you. The guide will probably answer any question you have on the fuel supply system.

Did Wes say there was anything wrong with the pump you returned? I kind of doubt it. He probably sets the fuel cutoff solenoid about 10 turns in, which is a good starting point (probably just a tad rich to begin with). The car should run fine with 10 turns in.

If it's indeed running lean, and you've confirmed it by spark plug appearance, I'd say check:

1. T/A good and adjusted correctly. Pump gap at .019" at 175 degrees.

1. Idle stop screw adjustment. This is the starting point for the syncronizing the throttle openings and the injection pump fuel delivery. The long arm pivot on the throttle bell crank should be 10 deg above the horizontal line.

2. Short rod. With the throttle bellcrank resting on the idle stop screw, the all throttle butterflies should be just closed (completely). The only air through the engine at idle should come through the idle air system (small hoses on manifold).

3. Long rod. Adjust so that with the engine completely hot (190 degees or so), the pump gap is .019". This is different than the setting the gap for the T/A. You set the T/A with a dummy acutator 27/29mm (depending on year) to.019" which basically simulates having a in-spec T/A in there at 175 degrees. As the engine gets warmer and reaches full operating temperature, the pump gap will get narrower and the throttle arm on the back of the pump will probably touch the reference screw. That's normal. There is no change in fuel delivery at less than .019" gap. You set the long rod so that you restore the pump gap back to .019". The rod ends can be up to 30 degrees offset from alignment in order to make fine adjustments.

[genericwood]

John, I continue to be baffled by the lean condition. Unfortunatlely, I may not be able to do much more until Spring. These Chicago winters are killing me! Since I have had the same problem with 2 Ingram pumps, I am 99.99% positive it isn't the injection pump. I checked fuel pressure this morning and it pegged the needle on the gauge which goes to 15psi. The pump timing has been checked multiple times. The gap is .019" at 175 degrees. The position of the throttle stops has been triple-checked as have the long and short rods. I set the mixture trying to achieve the best running condition at 2700rpm. The ignition has been completely gone through with new coil, new cap, new points, new rotor (nearly new wires). The valve timing and lash has been triple checked.

But the last time I ran it (with the 2nd injection pump), I still had what feels like a lean miss, and the plugs were white on a hot shutoff. With the first pump, I even went so far as to completely remove the cold start solenoid. It still ran lean! I thought it might be an intake leak but it idles too well.

Oh well, as soon as the snow and salt are gone, I will start over again!

Erik

[papajam]

Sounds like you've been very thorough in checking stuff. But what about fuel volume? Having good fuel pressure doesn't guaranty you're getting enough of it. Wes recommends a min. of .6 GPM. If you're not getting that much fuel, I'd check for an ailing fuel supply pump, partially plugged fuel filters, kinked supply side fuel hose(s), plugged fuel tank vent, etc.

[genericwood]

Good point, Jim. That will be on my list of things to check when things warm up!

Erik

[Roadtrip]

Eric - Sounds like the fuel supply is putting out good pressure. If the pump is building pressure quickly after key turn in the morning, the quantity rate is probably ok too.

1. You say that the car was running normally before you changed the pump. Right? But that even after installing the second overhauled pump from Wes, it still seems to run lean.
1. Have you put an induction timing light on the engine to see if you can visually see an ignition miss?
2. Have any weird fuel additives or gas tank cleaners/coating etc been in the fuel system?
3. Confirm that the intake manifold is on tight and no leaks?
4. Did you kink/crush any fuel pipes on the re-install?
*5. Confirm that you set the pump timing by putting the engine at TDC start of power stroke on the #4 (No. FOUR) cylinder, then rotating the engine counter clockwise to the "I" mark on the pulley, then lining up the indici on the pump body and pulley. This is real easy to goof up by inadvertently using the seemingly logical #1 cylinder. Sluggishness, flat spots, lots of throttle to maintain speed, chronically black tail pipe, & difficult to adjust mixture, are all symptoms of a mis-timed pump. Although, apparent rich running is a clue, not lean. Check it anyway.
6. Broken/leaking/misfit fuel pipes can lean out mixtures. Even a tiny leak could cause this due to the miniscule amount of fuel being injected on each cycle. Be care when checking them however, pressure in the pipes is 300-400 psi, so don't go around feeling them with your bare hand. If you didn't already, using a little anti-seize compound on the fuel pipe nuts will greatly aid their future removal.
7. If you power the CSS momentarily, does the engine go up in RPM or down (like it should)?
8. Do you note any difference in the rpm as you unscrew the Fuel Cutoff Solenoid toward rich? 9-10 turns in is the normal starting point and that's probably slightly rich. Try 5 turns and see if you get any more power and more normal spark plug color.

Past this Eric, I'm running out of ideas. At least in Chicago, I'm sure there are some good SPICA techs that you can take the car to if you get permanently stumped. Keep us posted and I'll keep thinking.

[genericwood]

Thanks John. I did check fuel volume today and it is fine. My problem now is that I refuse to take the car out of the garage onto wet/salty roads. So it may be awhile. The miss only occurs under some load, so I'm not sure I would see it on my timing light. I picked up new coil and plug wires today.

I asked Wes about the possibility of a leak on the injection to injector lines, even though all the fittings seem okay. His response is that they would leak fuel and not draw in air. None of them appear kinked, although I'm sure they have been bent a few times in their lives.

At least I have now eliminated a fuel supply problem. When I come out of my winter slumber, I will let the group know what I find. If I give up, I'll just take it to Mike Besic.

Erik

[Roadtrip]

I recently had a mysterious miss, very inconsistent, but more often under load. I could see an inconsistent miss/multi-fire even at idle on my induction timing light. Put new plug wires in and it was instantly cured. I've only had this car for a couple of years, so I don't know how old the wires were, but they looked good but worked bad.