well - I had a similiar cold start issue. tried many thing's but turned out to be the cold start valve. I wold check the resitance of the unit - and I'll try and get the ohms range - but mine way below spec (almost a short circuit, I assume over the years the insolation on the windings broke down) and it only stayed on for very short time when the computer called for it. Which reminds me it could be your engine temp sensor?