Chevy Bifuel pickup serious leak at HPR?

[kirkbenge]

My brother has a bi-fuel chevy pickup (I think it is a '00 chevy 3000 4X4, but I'll have to double check) Today while he was driving he heard a loud hissing, and got out to hear a major gas leak. The smell was strong, so he turned the car off to let it vent, but turning the car off stopped the leak. So he started it again, and the leak started up too. He then removed the CNG fuse, and started on gasoline, this time no leaking CNG.

Does anybody know from experience where the leak might be? I'm sure it must be either at the High Pressure Regulator, or in the line after the HPR, since pulling the fuse stopped the leak. The weather is cold in Salt Lake City, and I'm wondering if it's possible that he had damaged coolant lines, so some moisture could have frozen in the HPR or something, and caused a break. Where exactly is the HPR on one of these pickups anyway? I wasn't sure, and we couldn't really tell for certain where the leak was by listening.

Kirk

[Lancer Automotive Group]

Re: Chevy Bifuel pickup serious leak at HPR?

What system does his truck have on it.

[kirkbenge]

Re: Chevy Bifuel pickup serious leak at HPR?

Ok, so the truck is actually a '00 chevy K2500 4X4 factory install, so I don't know what system that is, but I'm sure someone does. (IMPCO?)

Anyway, here is the weird thing: it fixed itself today. It is no longer leaking, but it still has lots of CNG in the tanks. So what could it have been? It definitely wasn't leaking under the hood, and it wasn't leaking from the fill port either. I assumed it must have been at or near the HPR, but would their be an electronic venting system that could have malfunctioned? Does the HPR itself have a vent? How do we keep it from happening again? Anyone have any ideas?

[BruceEB]

Re: Chevy Bifuel pickup serious leak at HPR?

sounds like high pressure regulator located on drivers side inside of frame rail right in front of drivers door

[kirkbenge]

Re: Chevy Bifuel pickup serious leak at HPR?

Well, it's been five days with no problems. I'm wondering what, if anything, we should check. We're fairly certain that the leak was from the HPR, but we aren't sure if it's worth pulling apart... still wondering... hate to just wait to see if it happens again though

[kirkbenge]

Re: Chevy Bifuel pickup serious leak at HPR?

The truck started leaking again recently, so I think we will start by replacing the HPR. I assume at this point that there must be a pressure release valve somewhere along the "low" pressure line (between the HPR and LPR), either on the low pressure side of the HPR, in the line itself, or on the higher pressure side of the LPR. The HPR must somehow be malfunctioning occasionally, and letting too much pressure into that line, which then opens the pressure release valve.

Since this appears to be an IMPCO factory install, I think that I will use the handy guide provided by dovh49 as found here:How to install IMPCO HPR 3600 vs HPR 3600-GMC, bearing in mind that this for a Cavalier, and may be somewhat different on this truck. I'll let you all know how it goes.

[larrycng]

Re: Chevy Bifuel pickup serious leak at HPR?

Under NFPA 52 (4.7.2) the HPR has to have some means to protect the low pressure side of the system if there is a failure in the hight pressure side. Many regulators have a vent port for this purpose that should be vented in a safe direction

Larrycng

[CH-4]

Re: Chevy Bifuel pickup serious leak at HPR?

My brother has a bi-fuel chevy pickup (I think it is a '00 chevy 3000 4X4, but I'll have to double check) Today while he was driving he heard a loud hissing, and got out to hear a major gas leak. The smell was strong, so he turned the car off to let it vent, but turning the car off stopped the leak. So he started it again, and the leak started up too. He then removed the CNG fuse, and started on gasoline, this time no leaking CNG.

Does anybody know from experience where the leak might be? I'm sure it must be either at the High Pressure Regulator, or in the line after the HPR, since pulling the fuse stopped the leak. The weather is cold in Salt Lake City, and I'm wondering if it's possible that he had damaged coolant lines, so some moisture could have frozen in the HPR or something, and caused a break. Where exactly is the HPR on one of these pickups anyway? I wasn't sure, and we couldn't really tell for certain where the leak was by listening.

Kirk

I had the same problem on my 00 K2500 about 6 months ago. Lift the hood locate the fuses and pull the spaded fuse marked "CNG". The leak will stop as soon as the vehicle restarts, but on gasoline. The High Preasure Regulator needs to be changed, available from GM. Sit down before you get the price though, as it is a new OEM part.

[kirkbenge]

Re: Chevy Bifuel pickup serious leak at HPR?

Thanks CH-4. We actually already replaced the HPR. While it is true that it is expensive to buy original OEM HPR's we found out that we could actually buy an HPR at a local retail propane shop. IMPCO parts are sold under the distributor TEECO, and the HPR 3600-GMC part is the same as the HPR 3600 sold through TEECO. My brother found one on ebay for under two-hundred, and then took it to a local CNG mechanic to install (the only downside was that the threads weren't the same, otherwise we would have done it ourselves, but we needed an adapter, and didn't know what thread size we needed to adapt to, but our mechanic did).
Works like a charm now.