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Originally Posted by EEAllen

the flame sensor needs to get very hot in order to allow the gas valve to open for main flame...

This is especially true for the sensor bulb for the hydraulic safety valve the OP has in his deck oven. The pilot should get that sensor bulb glowing a cherry red.

Originally Posted by EEAllen

most of the time, gas pressure doesn't come into play when it comes with kitchen equipment, unless the gas valve is bad.

I'm stumped by that suggestion. Gas pressure is ALWAYS my first consideration when there's failure to ignite a main burner and gas pressure could cause it - whether the flame management system is:
1) A hydraulic safety valve such as the OP's deck oven has
2) A TS11 or BASO pilot safety valve employing the low millivolt DC output from a thermocouple
3) A combination valve requiring the much higher millivolt DC output from a thermopile, or...
4) An electronic ignition control that puts an AC signal to a "flame sensor" electrode, by which the ignition control acknowledges proper flame through flame rectification.

Proper, adequate and unfaltering gas pressure should ALWAYS be verified as a matter of proper troubleshooting practices and ESPECIALLY when there's doubt about it. Manufacturers will always want to know it when I'm called upon to do warranty calls.

In this situation, the "doubt about it" in the OP's situation was his observation that "The pilot flame is on, but when he turns the thermostat up the flame gets smaller and the oven won't fire up." I can't say I had the exact solution to his problem since he never gave feedback, but I'm very certain that I led him in the right direction.

Just yesterday I had a griddle do the same thing as the OP's oven. The problem was the pressure regulator was shrouded in grease and therefore had a clogged vent. This is a V-E-R-Y common problem with kitchen equipment due to the regulator's proximity to grease spatter.

Originally Posted by EEAllen

check these two:
1) take out the flame sensor, and clean it, sanding it off will work
2) take the pilot apart, see if the pilot line is clogged, blow on it to clear clog

I agree with both - although emery cloth, followed with a scotchbrite pad would be preferred for cleaning a flame sensor. However, the OP's oven doesn't have that type of flame sensor. I believe that, in your recommendation, you're referring to a flame sensor used on an electronic ignition system. Those are susceptible to oxidation and silicone migration - both of which can set up a resistance in the flame rectification circuit sufficient enough to prevent proper DC µA signal back to the ignition control module.
Cleaning a thermocouple, a thermopile or a sensor bulb on a hydraulic safety valve with sandpaper? I've never seen a situation where I thought that would be a viable solution. If so, then there's other problems. All that those components have to do is get sufficiently hot.

the flame sensor needs to get very hot in order to allow the gas valve to open for main flame, here's the two things that usually solve the problem, most of the time, gas pressure doesn't come into play when it comes with kitchen equipment, unless the gas valve is bad. check these two:
1) take out the flame sensor, and clean it, sanding it off will work
2) take the pilot apart, see if the pilot line is clogged, blow on it to clear clog

Originally Posted by ECtofix

Check condition of your line regulator. Sometimes the vent becomes clogged from grease and it won’t allow proper volume of gas to flow. I recommend you check your gas pressures too.

Often times, a pressure problem is evidenced by a distinctly diminished pilot flame when the thermostat calls for heat. Sounds like that’s happening to you and you’re getting gas to the main burners – but not enough to sustain a flame.

FYI: Unless that oven has already been converted to a TS11 or BASO safety valve, that oven uses a hydraulic safety valve. Therefore it doesn’t have a thermocouple. Instead, its sensing bulb and capillary contain mercury and is a permanent part of the safety valve.

The last I checked, they quit making those hydraulic valves some years ago. So, if you ever determine one of these hydraulic safety valves to be bad, then there’s probably a conversion kit from the oven manufacturer to one of the styles I mentioned that DO use a thermocouple.

Ditto
A good way of checking the vent plugs is just by removing them. If the oven fires up, you'll know its clogged.

i would also check gas pressure first. verify call for heat from stat.

Check condition of your line regulator. Sometimes the vent becomes clogged from grease and it won’t allow proper volume of gas to flow. I recommend you check your gas pressures too.

Often times, a pressure problem is evidenced by a distinctly diminished pilot flame when the thermostat calls for heat. Sounds like that’s happening to you and you’re getting gas to the main burners – but not enough to sustain a flame.

FYI: Unless that oven has already been converted to a TS11 or BASO safety valve, that oven uses a hydraulic safety valve. Therefore it doesn’t have a thermocouple. Instead, its sensing bulb and capillary contain mercury and is a permanent part of the safety valve.

The last I checked, they quit making those hydraulic valves some years ago. So, if you ever determine one of these hydraulic safety valves to be bad, then there’s probably a conversion kit from the oven manufacturer to one of the styles I mentioned that DO use a thermocouple.

Vulcan oven 7019A1 wint fire up

the pilot flame in on , but when i turn my thermostat up the flame get smaller and the oven wont fire up ? , the thermostat is new and the thermocouple is in the flame ,so what could be the problem ?
thanks