RamJet 502... stumbling

[rockdogz]

Help, my motor is stumbling....

Ok, so I've never had any engine problems up to now, and the other night the family and I go on a cruise. We're coming home and all of the sudden I lose power. I'm able to make it to a parking lot and we notice that I have some coolant on the ground - maybe a quart. I'm thinking there was a leak somewhere, but I don't find one. It's dark so I call for a flatbed, but seem to be able to drive it around the parking lot ok.

I thought it may be a bad thermostat, but I tested it and it opens at about 180-185 or so. However, the coolant temp is getting up way over 200 which is unusual. Maybe a water pump issue? Strange on an engine with fewer than 2000 miles.



I have the Diacom RamJet diagnostic software, and ran the engine for a while and gathered some data. It was just idling, but I tried to rev it up a little to get the temp up there. The twin Spaals spun up and were working.

Here is the number of minutes the engine has run, and the coolant temperature:

0 107
1 108
2 126
3 145
4 153
5 206
6 212
7 212
8 212
9 216
10 218
11 218
12 221
13 226
14 229
15 234
16 238
17 239 (engine off)
18 231
19 221
20 210


The gauge inside showed even higher temps, approaching 250.

Most importantly, I'm wondering if these high temps would cause the engine stumble and lack of power due to the fuel injection system. If not, any ideas there? Things like a clogged fuel filter don't seem to be an explanation since it will run fine for a couple minutes until it heats up.

I'm also trying to figure out what the cause of the high temps could be... water pump maybe? I'm running the reverse flow Vintage Air Front Runner water pump.

Thanks for any ideas!!

[Vegas69]

Anytime an engine get's that hot your drivability is going to suffer. Your fuel rails are going to get hot and can effect the fuel before it gets through the injectors. Also, does your engine have a fail safe mode when it gets to hot? That will do it as well. The cooling deal is a little strange if your fans are coming on at the proper temperature? Look at your coolant to make sure it's clean and all green. Is your bottom radiator hose collapsing? Look for bubbles in the coolant. You can get a pump and pressurize the system to check for leaks and test the radiator cap.

[rockdogz]

Yep definitely the water pump....

[David Pozzi]

You can probably rob an impeller from an old pump, rebuilders have the old style cast impeller which I think is a better version.

I don't know why, but in road racing it seems big blocks have more water pump issues like drive hubs coming loose, or impellers failing.

[tomspo04]

Tom, The stumbling is definately attributed to the engine temp. Mine has done the same thing. Mine ran hot a couple of times due to a fan problem. Everytime it got hot, it stubled. One tiem it just shut down.

[DeltaT]

Check your timing too.

Jim