1958 4900 f.i. cold start question

[Rick E.]

What is a average amount of cranking time on a cold engine with a 4900 f.i. unit? My car takes about 4 cranking cycles about 20 second each. It seems to be alot of cranking time. I know this is a hard question to answer but would like to know what others cars do.

[Arthur T.]

Re: 1958 4900 f.i. cold start question

What is a average amount of cranking time on a cold engine with a 4900 f.i. unit? My car takes about 4 cranking cycles about 20 second each. It seems to be alot of cranking time. I know this is a hard question to answer but would like to know what others cars do.

This is way too much cranking. I assume you are a 283 / 250hp since you said 4900 instead of 4900R. When I had my '58, a 283/250 on the road, it would always start right up within a couple of seconds unless it had been sitting for many days. Then, it would take longer to start. I think the difference was available fuel in the high pressure pump. Once fuel got into the system, it would start right up cold or warm.

I think you aren't getting fuel to the injector nozzles quickly on a cold start. If that is the case and your car has not been sitting for many days, then you need to have the FI serviced. It also suggests you might not have any of the the anti-siphon fixes in your 4900.

John DeGregory lurks here regularly. He is one of the experts on these units and could give you better advice. There are other knowledgeable folks out there as well, Jerry Bramlett and Jim Lockwood come to mind.

[Jim L.]

Re: 1958 4900 f.i. cold start question

Rick, how long has your car been sitting when you have to do four 20 second cranking attempts?

If several weeks or months, that's not an unreasonable amount of cranking. If over night to perhaps as much as a week, you should expect the engine to fire within about 10 revolutions.

If your 4900 unit still utilizes a cranking signal valve, I would suspect that it has failed in an unusual (but not impossible) way. The valve should open once the engine shuts off and it should remain open until the engine fires again. My hunch is that your CSV is remaining closed all the time. This isn't the common failure mode for a CSV, but it happens.

John D. can supply you with a replacement.

Jim

[Rick E.]

Re: 1958 4900 f.i. cold start question

Jim, The engine crank time is about the same if it sits over night or a month. Thanks for your help. Rick

[John D.]

Re: 1958 4900 f.i. cold start question

Rick, Pull out your dipstick and see if you can smell gas. Also check the oil level at the same time. The 4900 unit is notorious for dumping gas into the engine. They are even worse than the '57's for bending connecting rods and blowing engines.
Hopefully by this time that FI unit has a siphon breaker kit installed. That's a shut off solenoid kit that goes between the spider and the fuel bowl.
If not put on one.
Now here is a trick for you. Lockwood gave you good advise. But say your Cranking signal valve is all right, and say you have a shut off solenoid installed and the FI is still hard to start. Now I am assuming (bad word) that your ignition system is dead nuts or that could be a culprit.

Remove the felt filter from the choke housing. When the engine is ice cold look inside this housing with a flashlight. I dont' know if I can type this all or not but I will try.
Backing up. Do you have the shop manual for your car. Buy the Corvette Servicing Manual from NCRS, etc. In it is the worlds best fuel injection info.
Look in the theory section. Notice your cold enrichment housing (choke housing). See the two pins inside the housing. One is fatter than the other. The fat pin is closest to the fender and is called the power boost pin. It's used to starting as it sends out a strong signal to the fuel meter (fuel bowl).
ABC's of FI is this. The air meter tells the fuel meter what to do.
So your job is to rotate the black plastic cover clockwise a tad so the power boost pin is depressed about 1/3 or 1/4 of the way in. Then carefully tightne up the three retaining screws of the cover.
Now try and start the engine. It may start a lot easier. Now if the big pin is depressed too much for too long that means you have rotated the cover to far. So back off a notch or so. Let me try that again. If your have the power boost pin pressed in too far the car will run very rich at idle. To help this don't push it in so far-meaning rotate the cover counterclockwise a notch or two.
Don't pay attention to the manual when it states how many notches you need to adjust a choke cover on aa 57 to 65 FI. That's lot of crap. Just do it by the seat of your pants.
If you have vacuum leaks, bad hoses, warped main diaphragm cover, spill valve issues, etc. All of that will contribute to hard starting. If you ethanol is over 3 or 4 months then that is no good. If your spark plugs, coil and the rest of the ignition system is not correct that will contribute to hard starting.
Look in the trouble shooting section of the Corvette Servicin Guide FI section. Holler if you need more info. John

[Rick E.]

Re: 1958 4900 f.i. cold start question

Guys ,Thanks for your comments! I am not able to look at the car at this time but will soon. I understand what you are telling me and will look it over and report back. I do have the soleniod and the injection is completely rebuilt and runs great after it starts. I have never driven this car yet and just got back to address the hard starting problem and finishing the frame off restoration.

[Tom P.]

Re: 1958 4900 f.i. cold start question

I have NEVER timed how long it takes to start the engine on the 56 after it has sat for an extended time (2wks and longer), but it always has to be cranked for a while. Also, this is quite common on FI engines (Yes, I have a 56 with FI).
Well, after reading all of the above, I went out to time from first crank to start. I almost never continually crank until it starts. I crank it in (about) 5sec bursts, wait about 5sec and repeat until it starts. Today, after the car had sit for about 1mo, it took about 30sec before it started, which was similar to past starts after the car has been sitting for a while. If it has been 1-2 days since starting, then it usually fires right off with VERY MINIMAL cranking.
My unit has had some upgrades (most people would call them modifications), but it is fundamentally a 62 unit. The cranking signal valve (which can fail if the tiny internal diaphragm ever ruptures) has been replaced with a Skinner valve (elec solenoid) which still performs the exact same function as a cranking signal valve. And a few other changes/upgrades have been done. Once started, it performs as well or better than Rochester ever designed.

[Rick E.]

Re: 1958 4900 f.i. cold start question

I have been out of town awhile and have been playing with the injection. I came home and remembered that the fast idle cam screw would not give me very much r.p.m. because the screw came up tight to the spring (home made). I removed the screw and spring, installed the fast idle cam screw without the spring ,adjusted the screw for more r.p.m. and the engine started in about 5 sec. after sitting for over three weeks. I have started it three different days after the fix and each time it fires up great. Thanks for the help and advise. Rick

[Bruce W.]

Re: 1958 4900 f.i. cold start question

What is a average amount of cranking time on a cold engine with a 4900 f.i. unit? My car takes about 4 cranking cycles about 20 second each. It seems to be alot of cranking time. I know this is a hard question to answer but would like to know what others cars do.

Rick I own two fuel cars. Here is the secret to staring and not fouling the plugs. Crank for four seconds then stop for four seconds. It should start by the 3rd try. Let me know if it works. Bruce Wilcox

[Brady C.]

Re: 1958 4900 f.i. cold start question

My 58 (4900 - 250 hp fuelie) takes about 20 seconds to start after setting the choke after the car has been setting up for 2 months or so. I found that keeping the car in a climate controlled environment, avoid ethanol at all cost and not monkey with any of the settings - works best. Car has started this way everytime during the 10 years i have owned.

As i have always been told on a PV, depress the accelerator one time to set the choke, then crank and you can't stop cranking (turning the engine over) before it starts or you fail that portion of the PV on a cold start.... and / or take the chance you miss you high idle.... another PV issue.... Hard not to want to pump the accelerator but as John says, quickest way to dump fuel and then that leads to other problems... Just takes a strong battery as i make sure i always start the same way...

Brady Como
# 42793

[Jim L.]

Re: 1958 4900 f.i. cold start question

. Hard not to want to pump the accelerator but as John says, quickest way to dump fuel and then that leads to other problems...

I think you've misunderstood what John was trying to say.

Pumping the accelerator doesn't cause the FI unit to dump fuel. In fact, it doesn't do anything at all except cause the throttle plate to open and close because there is no accelerator pump on an FI unit.

Said differently, it doesn't hurt anything to pump the accelerator; it just doesn't do any good.

John's comment about the 4900 dumping fuel was a reference to a fuel siphoning issue which wasn't well understood by RP when the 4900 unit was manufactured. The electric anti-siphon valve which is customarily retrofitted prevents the siphoning problem from happening.

Jim