Lengthy cranking on cold start with FI

[G B.]

I've been testing to determine why some '58 - '63 FI units are hard to start cold. Since these units are equipped with a Cranking Signal Valve, I used to assume the CSV was always linked to the problem. I was wrong.

I don't fault anyone for being suspicious of their CSV. It's a very clever design (in theory) that just doesn't hold up well under real world conditions. However, I've found CSV's almost always fail "open" rather than "closed". Then could they still function but shut off the signal boost too soon? Well, I guess it's possible. I've seen that happen myself, but I think it was a once-in-a-lifetime event for me.

Could the engine be generating an especially low vacuum level during cranking? Yep, that's possible, but it's unlikely. I've tested an engine with a 50% leak-down rate, a 30-30 cam, and a slow starter. It still managed to generate a 1" manifold vacuum during cranking, and that's enough to start if.... YOU HAVE TIGHT CLEARANCES IN THE GEAR PUMP.

Unfortunately, the gear pump is the culprit in most of these hard cold starting cases. At the slow speed of cranking, you've got to have extremely tight clearances between the gears and the pump center housing / end plate to generate a good nozzle spray. I'm talking on the order of less than .001" clearance. Otherwise the pump just won't send enough gas pressure to the nozzles to make the engine start.

There isn't any way to repair a worn gear chamber now. There are no replacement gears and center housings available with the necessary close tolerances. The good news is that some are on the way, probably. I'm not making them, but Gail Parsons is planning to do so. I'll post more news when I have it. No, I don't know when they'll be ready for sale.

I've given poor advice to some about this hard starting problem in the past. I apologize for that. I know better now, I think. You just can't eliminate the problem unless you convert your unit to a '57 / '64-65 type solenoid design using engine fuel pump pressure for starting. But... a temporary cheap fix is to keep a can of ether near the car just for cold starts.

[Pat L.]

Re: Lengthy cranking on cold start with FI

Jerry,

You and I have had this discussion many times because as you remember my FI was taking a long time/many turnovers to crank. The new starter from Mr. Pirkle made a big difference. However, the can of ether works when the car has sat for a long time during the winter months. Regardless, as a straight shooter, again you tell it like it is. Very refreshing. I don't think you need to apologize for giving poor advice on this issue. Through continuous research and hands on experience, these things come to light, but guys like you are man enough to pass it on after thinking for a long time that there was something else causing the problem. For all of the advice and information that you have provided to me and a lot of other people, you have NOTHING to apologize for. Thanks for all of your help and your patience when having to put up with all of the dumb questions from us.

[Duke W.]

Re: Lengthy cranking on cold start with FI

I have a general idea of how the gear pump is laid out, but have never taken one apart.

For oil pumps, it's good to dress the housing down to achieve no more than two thou end play. This will help the pump build pressure at low speed by minimizing internal leakage.

AFAIK the FI pressure pump is basically the same type, so mimimizing gear end play should accomplish the same end.

The FI unit's Achilles heel is low cranking and idle fuel pressure, which I believe is the source of idle "problems" and many starting problems.

I have some experience with a similar system - the Bosch KE Jetronic on my Mercedes. It's also a continuous flow type, but the "nozzles" incorporate a check valve, which requires about 5 bar to open. Thus idle fuel pressure is fairly high and is provided by an electric pump. The valves are also designed to "chatter" - rapidly open and close, which improves fuel atomization.

Despite the above "enhancements" the engine exhibits idle roughness that I attribute to uneven fuel distribution, and I also believe this is the cause of the relatively high HC emissions of KE-equipped Mercs. An inline six should idle butter smooth, and I've been in old Chevys sixs that idled smoother than my Merc.

Continuous flow injection is okay for power (It was successfully used in many large aircraft engines.), but no one has ever gotten a continuous flow system to idle as well as a well sorted out carburetor much less a modern system with solenoid injectors.

Duke

[Verle R.]

Re: Lengthy cranking on cold start with FI

Jerry,

I would think a high quality machine shop could mill/grind the housing and gears to the required tolerance for end play. What about gear teeth/body clearance tolerance?

Verle

[G B.]

Other causes and cures

You're welcome, Pat.

You brought up some other causes that I should have mentioned. The easiest problem to fix is a slow cranking starter. Even Delco/Delphi still sells a good high torque starter motor. Also, the gas in the fuel meter bowl can evaporate over time. Then the engine has to be cranked long enough to submerge the gear pump inlet in order for the pump to work.

Another common problem is leakage at the fuel meter anti-siphon "pill" valve. This valve is an internal safety device to prevent hydraulic lock (gas siphoning out of the fuel meter and into a cylinder while the engine is off). I've noticed that these pill valves always leak a little at low gear pump speeds. Evidently the flow isn't strong enough to push the little aluminum ball inside up against the air bleed port at the top of the valve. You can remove the pill valve and seal the hole in a '60 - '62 unit AFTER YOU'VE INSTALLED AN ELECTRIC SOLENOID FUEL SHUT-OFF BETWEEN THE SPIDER AND THE FUEL METER. However, you can't install such an electric solenoid on a '63 unit because of the different spider design, so this pill valve fix isn't available to you.

I've had some success with a temporary modification to the gear pump itself. GM installed a tiny pressure bleed hole in the back plate of all FI gear pumps. I assume this was done to limit the damage possible when a positive displacement type pump is dead-heading (discharging into a closed system). When this bleed hole is filled, pump pressure leakage is reduced considerably, but this is not a fix that I would leave in place forever.

What a pain in the butt. You can see why most owners choose to buy a $3 can of starting ether every two years rather than try to fix the root problem. I don't blame them a bit.

[G B.]

Re: Lengthy cranking on cold start with FI

Gear end play is seldom the problem, and it's easily repaired when it is.

The loose clearance that can't be fixed is between the gear teeth and the inside walls of the pump center housing. Such excessive wear often results from the center housing being installed backwards by a Do-It-Ur-Selfer. They ignore the stiff resistance to turning that results and just put the pump back into service. A hundred miles later, they've got a worn out pump center housing.

[Mike McKown]

I had come to the conclusion

that the best way out of my "perceived problem" of a slow cold start was go to a faster cranking starter motor. It seems that starter motors from the '60's era are no load rated from about 4500 to 12000 rpm. There is also an amp load rating but.................... Well, let's just say that I learned ohm's law in 7th grade shop class and forgot it the next year. Some 6 cylinder starters spin much faster than the 327's. The 409's spin about as fast as the six cylinders. These are no load rpm's. So, in order to get the fastest Delco starter motor, do I need to get one of the hi-torque jobs? Can I mix/match some Delco parts to get something quicker? How about the aftermarket mini-starters? Seems like I see A LOT of these things for sale at swap meets. See them at rebuild shops too.

My engine does a cold start without help. It's more embarrassing than anything.

Anybody have any ideas?

[Clem Z.]

check to make sure your battery cable

is pure copper not copper plated alumium. attach the battery ground cable to bolt that attaches the starter to the block for good ground. the GM high torque starters have about 1 inch of the main body extending past where the lead goes from the solenoid into the starter fields,the std starter has the lead going in at the end of the starter case.

[Mike McKown]

I understand the value of copper cable and a good

along with a starter motor in good condition. What I'm asking is simply what starter motor will crank a 327 engine faster than the next one or what to do to a starter to make it crank faster. Strictly focusing on the starter motor. I've never noticed a Delco hi-torque starter actually cranking an engine any faster than the standard length field coils and armature. Maybe they do.

[Dick W.]

Re: check to make sure your battery cable

Have John Pirkle build you a starter with the welded armature. We have one on a 72 454, built as an iron head LS 6, compression and all. Starts just as well hot as it does cold.